Ag-Pb-Sb Sulfosalts and Se-Rich Mineralization of Anthony of Padua

Article Ag-Pb-Sb Sulfosalts and Se-rich Mineralization of Anthony of Padua Mine near Poliˇcany—Model Example of the Mineralization of Silver Lodes in the Historic Kutná Hora Ag-Pb Ore District, Czech Republic

Richard Pažout 1,*, Jiˇrí Sejkora 2 and Vladimír Šrein 3

1 Institute of Chemical Technology, Technická 5, 166 28 Prague 6, Czech Republic 2 Department of Mineralogy and Petrology, National Museum, Cirkusová 1740, 193 00 Prague 9–Horní Poˇcernice,Czech Republic 3 Czech Geological Survey, Klárov 3, 118 21 Prague 1, Czech Republic * Correspondence: [email protected]; Tel.: +420-220444080

Received: 3 May 2019; Accepted: 6 July 2019; Published: 12 July 2019

Abstract: Significant selenium enrichment associated with selenides and previously unknown Ag-Pb-Sb, Ag-Sb and Pb-Sb sulfosalts has been discovered in hydrothermal ore veins in the Anthony of Padua mine near Poliˇcany, Kutná Hora ore district, central Bohemia, Czech Republic. The ore mineralogy and crystal chemistry of more than twenty silver minerals are studied here. Selenium mineralization is evidenced by a) the occurrence of selenium minerals, and b) significantly increased selenium contents in sulfosalts. Identified selenium minerals include aguilarite and selenides naumannite and clausthalite. The previously unknown sulfosalts from Kutná Hora are identified: Ag-excess fizélyite, fizélyite, andorite IV, andorite VI, unnamed Ag-poor Ag-Pb-Sb sulfosalts, semseyite, stephanite, polybasite, unnamed Ag-Cu-S mineral phases and uytenbogaardtite. Among the newly identified sulfides is argyrodite; germanium is a new chemical element in geochemistry of Kutná Hora. Three types of ore were recognized in the vein assemblage: the Pb-rich black ore (i) in quartz; the Ag-rich red ore (ii) in kutnohorite-quartz gangue; and the Ag-rich ore (iii) in milky quartz without sulfides. The general succession scheme runs for the Pb-rich black ore (i) as follows: galena – boulangerite (– jamesonite) – owyheeite – fizélyite – Ag-exces fizélyite – andorite IV – andorite VI – freieslebenite – diaphorite – miargyrite – freibergite. For the Ag-rich red ore (ii) and ore (iii) the most prominent pattern is: galena – diaphorite – freibergite – miargyrite – pyragyrite – stephanite – polybasite – acanthite. The parallel succession scheme progresses from Se-poor to Se-rich phases, i.e., galena – members of galena – clausthalite solid solution – clausthalite; miargyrite – Se-rich miargyrite; acanthite – aguilarite – naumannite. A likely source of selenium is in the serpentinized ultrabasic bodies, known in the area of “silver” lodes in the South of the ore district, which may enable to pre-concentrate selenium, released into hydrothermal fluids during tectonic events. The origin of the studied ore mineralization is primarily bound to the youngest stage of mineralization of the whole ore district, corresponding to the Ag-Sb sequence of the ‘eb’ ore type of the Freiberg ore district in Saxony (Germany) and shows mineralogical and geochemical similarities to low-sulfidation epithermal-style Ag-Au mineralization.

Keywords: Ag-Pb-Sb sulfosalts; selenium-rich mineralization; Kutná Hora; clausthalite; naumannite; andorite group; argyrodite; Ag-Sb(-Au) alloys; acanthite – aguilarite; succession

Minerals 2019, 9, 430; doi:10.3390/min9070430 www.mdpi.com/journal/minerals Minerals 2019, 9, 430 2 of 47

1. Introduction Kutná Hora was one of the best-known mining centres in Europe in the Middle Ages. In the first stage of mining (in the 13th and 14th century), the ores of silver-rich lodes in the southern part of the Kutná Hora ore district (Figure1a) were mined extensively. By means of the so-called fire-setting mining technique 500 m depth below the surface was reached as early as before the end of 14th century [1,2]. Before the end of the 15th century, mining activity moved from the silver-rich southern part of the Kutná Hora ore district (especially Oselské pásmo Lode) to the northern part of this district, which had silver-bearing sulfide “pyrite-rich” ores (especially Staroˇceské pásmo Lode at Kaˇnk,north of Kutná Hora) (Figure1a). The ores of the northern lodes (ore zones) were poorer in silver (200–300 g /t silver), but the veins were more massive and ore-abundant. Continually increasing operating costs and the discovery of cheaper silver from American deposits caused a decline of mining in Kutná Hora at the turn of the 16th and 17th century [2]. The knowledge of mineralogy of ore veins in the southern silver-rich part of the Kutná Hora ore district has so far been incomplete. Mining in this historically important part of the ore district ended in the 16th century and later explorations were carried out only on a very limited scale [3–8]. Therefore, mineralogical research of this part of the ore district had to rely only on occasional finds of primary mineralization on medieval mine dumps, mostly localized in areas built up by medieval town [8], but still partly preserved south of the historic centre of the town. Known silver minerals from southern lodes of the ore district include acanthite [9,10], allargentum [9,11], diaphorite [12,13], freibergite [13], freieslebenite [14], miargyrite [13,15], owyheeite [16], proustite [13], pyragyrite [13], pyrostilpnite [17], stephanite [11], silver [9],Au-rich silver and Au-bearing dyscrasite [11].No selenium minerals have been known, no selenium contents above detection limit determined. In northern lodes, the following silver minerals not occurring in southern lodes were described: canfieldite [18], gustavite [19,20] and matildite [21]. The pyrite-rich assemblage has recently yielded a rich suite of Ag-Pb-Bi-Sb sulfosalts. Recently identified minerals from northern lodes include terrywallaceite, vikingite, treasurite, eskimoite, erzwiesite, izoklakeite, aramayoite [22,23] and new mineral staroˇceskéite [24]. Minerals 2019, 9, x FOR PEER REVIEW 3 of 45

Figure 1.Figure(a) 1. Map (a) Map of theof the Kutn Kutnáá Hora ore ore district district with with major major ore lodes, ore adapted lodes, from adapted Malec fromand Pauliš Malec and [25]. Each lode (“pásmo” in Czech, “Zug” in German) consists of several veins. (b) map of Anthony Pauliš [25]. Each lode (“pásmo” in Czech, “Zug” in German) consists of several veins. (b) map of of Padua mine, Kutná Hora, adapted from Koutek and Kutina [26]. The blue-marked sections are Anthonyore of-mineraliz Padua mine,ed. Kutná Hora, adapted from Koutek and Kutina [26]. The blue-marked sections are ore-mineralized. 2. Geological Setting

2.1. Kutná Hora Ore District The Kutná Hora Ag-Pb-Zn ore district (60 km east of Prague, Central Bohemia, Czech Republic) represents a hydrothermal vein type mineralization of Variscan age [26]. The ore district covers the area of 10 × 5 km in N-S direction. Ore veins are clustered in so-called ore zones or lodes (“pásmo” in Czech), each 1 to 3 km in length and 100–500 m in width (Figure 1a). A detailed description of the geological and mineralogical situation of the Kutná Hora ore district is given in [25–27]. The genetical, geological, mineralogical and chemical similarities of the ore districts of Kutná Hora and Freiberg (Germany) have been studied and pointed out by several authors, e.g. [28,29]. In general, two mineral assemblages are present in the ore district: one “silver-rich”, developed in gneisses of the Varied unit of the Kutná Hora Crystalline Complex in the south, and the other “pyrite-rich” in gneisses and migmatites of the Malín unit in the north [25,26]. The silver-rich assemblage consists mainly of miargyrite, pyrargyrite, freibergite, freieslebenite, diaphorite, allargentum, native silver, galena, pyrite, sphalerite, berthierite and Pb-Sb(-Ag) sulfosalts (boulangerite, jamesonite, owyheeite) in quartz–kutnohorite gangue [25,27]. The pyrite-rich assemblage comprises pyrite, arsenopyrite, sphalerite, Ag-bearing galena, pyrrhotite, marcasite, chalcopyrite, stannite, freibergite and Pb-Sb-Bi-Ag) sulfosalts in quartz gangue without kutnohorite. The presence of Bi and Sn (each from a different mineralization sequence) is typical, while it is completely absent in the former, silver-rich assemblage. The pyrite-rich assemblage yields a rich suite of Ag-Pb-Bi-Sb sulfosalts, recently studied by Pažout [22,23].

2.2. Anthony of Padua Mine Near Poličany Anthony of Padua mine is situated south of Kutná Hora near the village of Poličany in the valley of the Vrchlice stream, about 200 m SSW of Kruchta Mine, which is the southernmost historically documented mine of the Oselské pásmo Lode, the largest “silver lode” of the medieval Kutná Hora ore disctrict. Geologically and mineralogically, the mine belongs to the Oselské pásmo

Minerals 2019, 9, 430 3 of 47

The small Anthony of Padua Mine, located near the village of Poliˇcanyin the southern part of the Kutná Hora ore district, has been preserved to this day owing to the renewed exploration mining during the World War II. Thus, the mine represents a unique opportunity to study in detail the mineralogy of Ag-rich ores both in dump material and also in situ, sampled in the ore veins uncovered inside the mine. Therefore, it is a very appropriate model example, providing a large abundance and variety of new information on the mineralogy of the southern part of the Kutná Hora ore district, including the newly discovered, previously unknown selenium mineralizations from Kutná Hora.

2. Geological Setting

2.1. Kutná Hora Ore District The Kutná Hora Ag-Pb-Zn ore district (60 km east of Prague, Central Bohemia, Czech Republic) represents a hydrothermal vein type mineralization of Variscan age [26]. The ore district covers the area of 10 5 km in N-S direction. Ore veins are clustered in so-called ore zones or lodes (“pásmo” in × Czech), each 1 to 3 km in length and 100–500 m in width (Figure1a). A detailed description of the geological and mineralogical situation of the Kutná Hora ore district is given in [25–27]. The genetical, geological, mineralogical and chemical similarities of the ore districts of Kutná Hora and Freiberg (Germany) have been studied and pointed out by several authors, e.g. [28,29]. In general, two mineral assemblages are present in the ore district: one “silver-rich”, developed in gneisses of the Varied unit of the Kutná Hora Crystalline Complex in the south, and the other “pyrite-rich” in gneisses and migmatites of the Malín unit in the north [25,26]. The silver-rich assemblage consists mainly of miargyrite, pyrargyrite, freibergite, freieslebenite, diaphorite, allargentum, native silver, galena, pyrite, sphalerite, berthierite and Pb-Sb(-Ag) sulfosalts (boulangerite, jamesonite, owyheeite) in quartz–kutnohorite gangue [25,27]. The pyrite-rich assemblage comprises pyrite, arsenopyrite, sphalerite, Ag-bearing galena, pyrrhotite, marcasite, chalcopyrite, stannite, freibergite and Pb-Sb-Bi-Ag) sulfosalts in quartz gangue without kutnohorite. The presence of Bi and Sn (each from a diﬀerent mineralization sequence) is typical, while it is completely absent in the former, silver-rich assemblage. The pyrite-rich assemblage yields a rich suite of Ag-Pb-Bi-Sb sulfosalts, recently studied by Pažout [22,23].

2.2. Anthony of Padua Mine Near Poliˇcany Anthony of Padua mine is situated south of Kutná Hora near the village of Poliˇcanyin the valley of the Vrchlice stream, about 200 m SSW of Kruchta Mine, which is the southernmost historically documented mine of the Oselské pásmo Lode, the largest “silver lode” of the medieval Kutná Hora ore disctrict. Geologically and mineralogically, the mine belongs to the Oselské pásmo Lode. The adit of the Anthony of Padua mine (situated at GPS: 49◦55.77858’ N, 15◦15.29307’ E) accesses ore veins that belong to the southern “silver-rich” Oselské pásmo Lode (Figure1a). The first mine workings in this area began probably already around 1300; written references about mining activity come from 1752–1755 [7,30,31] and 1769–1770 [32]. The last exploration works in the adit were undertaken in 1943–1945 [32]; at present, this abandoned mine is still partially accessible. Ore veins of the Anthony of Padua Mine are developed in gneisses of the Varied unit of the Kutná Hora Crystalline Complex, namely in proterozoic medium to strongly migmatized double-mica paragneisses with transition to migmatites with interbeds of muscovite-biotite othogneisss; the composition of wall rock has no or little influence on hydrothermal mineralization [32]. These rocks are classed as belonging to the Šternberk-Cˇ áslav Group established by [26] and [33]. In the central part of the Kutná Hora ore district, the rocks of the Crystalline unit are covered by Cretaceous and later Quaternary sediments, while in the valley of the stream of Vrchlice near PoliˇcanyCretaceous sediments are missing and Quaternary sediments are denudated. Anthony of Padua mine accesses five ore veins with strings in a zone or area 30–40 m wide (Figure1b), with a typical thickness of 20 to 50 cm (occasionally bulging to 1 m) and N–S to NNE–SSW Minerals 2019, 9, 430 4 of 47

direction. Therefore, some veins intersect, or are considered to be strings. Some dip 60 to 85◦ to the E, other to the W [32]. Vein gangue consists of quartz and kutnohorite with disseminated or massive sulﬁdes. The mineralogy of ores found in Anthony of Padua mine was systematically studied for the ﬁrst time by Koutek and Kutina [32], which was followed by another paper by Kutina [34], presenting the results of semi-quantitative chemical analyses. The results of shorter papers are summarized in [35] and newly in concise articles of [25,27,36]. Known silver minerals from the Anthony of Padua mine include: miargyrite, pyrargyrite, freibergite, diaphorite, freieslebenite and silver. Until now, only contents of Se up to 0.14 wt.% were found [35] in galena from Anthony of Padua mine.

3. Sampling and Analytical Methods The studiedore samples were collected in situin the adit of Anthony of Padua mine (Figure1b), from spots described in Section 4.1. Samples for microscopy and following laboratory study were prepared as polished sections 2.54 cm in diameter, mounted in resin and polished with diamond suspensions. The ore minerals and textures were studied in reflected light using a Nikon Eclipse ME600 polarizing microscope in the National Museum, Prague. Seventy polished sections, prepared from a representative number of ore specimens collected during field work in 1999–2015, were investigated microscopically and subsequently analysed on two different electron microprobes (3000 point analyses altogether). Quantitative chemical analysis was performed with Cameca SX electron microprobe (EPMA, National Museum, Prague), WDS analysis, operated at 25 kV, 20 nA, and a beam diameter of 2 µm. The following standards and X-ray lines were used: Ag (AgLα), CdTe (CdLα), CuFeS2 (CuKα), FeS2 (FeKα, SKα), NiAs (AsLβ), PbCl2 (ClKα), PbS (PbMα), PbSe (SeLβ), Sb2S3 (SbLα) a ZnS (ZnKα). Raw intensities were converted to the concentrations of elements using automatic “PAP” matrix-correction software. The second portion of polished sections (incl. Au-rich silver) was analysed with the electron probe microanalyser JEOL JXA-8530F at Institute of Petrology and Structural Geology, Faculty of Natural Sciences, Charles University, Prague. Accelerating voltage was 20 kV, beam current 20 nA and electron-beam diameter 1 µm. The following standards and X-ray lines were used: Au (AuLα), Ge (GeLα), cuprite (CuKα), cinnabar (HgLα), Bi2Se3 (SeLα), Ag (AgLα), Sb2Te3 (TeLα), stibnite (SbLα) and marcasite (SKα). Measured data were corrected using ZAF method. Peak-counting times were 20–30 s and one-half of the peak time was used for each background. The contents of the above-listed elements, which are not included in the tables, were analysed quantitatively, but their contents were below the detection limit (ca. 0.01–0.04 wt.% for individual elements).

4. Mineralogy and Mineral Chemistry—Results

4.1. Characterization of Ore Mineralization of Anthony of Padua Mine The majority of the studied material comes from Vein B (Figure1b), with a thickness of 20–60 cm, NNE–SSW direction and dipping 65◦ to the East. Two basic kinds of ore mineralization were found in this vein: (i) Pb-rich (so called “black ore”) and (ii) silver-rich (so called “red ore”), diﬀering in associated minerals, prevailing and present elements and gangue minerals. Black ore (i) is formed by massive or disseminated grain aggregates (up to the size of 15 cm) consisting of galena, miargyrite, massive Pb-Sb sulfosalts (boulangerite, jamesonite) and pyrite in quartz gangue and fewer carbonates (kutnohorite). Accessory minerals include freibergite, sphalerite, Ag-Pb-Sb sulfosals (diaphorite, freieslebenite, minerals of the andorite series, owyheeite). Selenium is present in members of galena–clausthalite solid solution. Minerals 2019, 9, 430 5 of 47

On the other hand, the Ag-rich red ore (named after its marked colour)—ore (ii)—consists of grains of miargyrite up to 5 centimetres across, associated with pyrargyrite, freibergite, with crystals up to 5 mm in occasional cavities, small metallic outgrowths of native silver up to 3 mm, coarse-grained sphalerite and massive pyrite in kutnohorite and quartz. Ag-Pb-Sb sulfosalts are rare or non-present (no andorite group minerals). Accessory minerals include aguilarite, selenides naumannite and clausthalite, high-grade silver minerals (stephanite, acanthite), germanium is present in argyrodite and Au occurs as Au-rich silver (electrum) and Au-rich dyscrasite. Another portion of the studied material, representing ore (iii), comes from the intersection of the vein I and the vein A (Figure1b); the main vein I, with a thickness of 20–80 cm, N–S direction and dipping 65–80◦ to the E, cuts and shifts by several decimetres a diagonal vein A with the thickness of 20–40 cm, NE–SW direction and with dips of 35–65◦ to the SE. The prevailing mineral is miargyrite in milky white quartz, the sparse associated base sulfide (if it occurs) is pyrite. Miargyrite forms massive grains, bands and veinlets up to several cm in size and well-developed crystals in quartz cavities, usually several mm in size. The maximum size of individual crystal exceeds 1 cm. Often, thin red fillings of miargyrite in fractures and fissures in quartz occur. Miargyrite is accompanied by less frequent pyrargyrite, freibergite, pyrostilpnite, diaforite and freieslebenite.

4.2. Pb-Sb-Ag Sulfosalts

4.2.1. Diaphorite Ag3Pb2Sb3S8 Diaphorite is a frequently occurring mineral in studied material (200 point analyses). It was found as anhedral grains up to 150–200 µm in size, most often associated with galena, freieslebenite, boulangerite, freibergite, jamesonite and andorite group minerals in black ore (i) (Figure2a–e). In the general succession that follows the trend from Pb-rich phases to Ag-rich phases, it is usually a later mineral than freieslebenite and is replaced by freibergite or miargyrite. Macroscopically, visible to naked eye, diaphorite forms lead to steel grey striated crystals up to 3 mm in quartz cavities (occasionally tarnishing black or bronze) and grain aggregates several mm in size in quartz gangue of ore (iii) (Figure2f) or kutnohorite–quartz gangue of red ore (ii). The chemical composition of diaphorite from the Anthony of Padua mine (Table1) shows a considerable variation in Ag/Pb ratio in the range 1.47–1.80. Mozgova et al. [37] describedthe compositional variation in diaphorite on the basis of microanalytical and crystal structure data from various diaphorite occurrences. They speculated on a continuous solid solution series between diaphorite and a phase with the formula Ag2PbSb2S5 (old unvalid name “brongniardite”) and considered that this phase with Ag/Pb ratios between 1.75 and 2.00 may be an Ag-rich diaphorite. This argument would be supported by the study of diaphorite from Herja (Ag/Pb 1.53–1.69), Rumania [38] or Apuan Alps (Ag/Pb 1.67), Italy [39]. On the other hand, the published data for diaphorite from Kutná Hora [12,35] or Pˇríbram [40] show compositions close to ideal stoichiometry (Ag/Pb 1.44–1.54). The detected range of SSe 1 substitution is limited to 0.29 apfu Se (1.71 wt.%). The maximum contents − of Se were found in samples with Ag/Pb ratio about 1.6. Traces of As were also determined.

4.2.2. Freieslebenite AgPbSbS3 Freieslebenite is fairly common in the studied assemblage (200 point analyses), it occurs as anhedral grains up to 60 100 µm in size in black ore (i) in association with boulangerite, owyheeite, × galena, diaphorite and miargyrite. Freislebenite is a later mineral than galena and it is replaced by later diaphorite, miargyrite and minerals of the tetrahedrite groups (Figure2a–c). Macroscopically, freieslebenite was found as striated steel grey or black metallic crystals up to 2 mm in quartz cavities or grain aggregates in ore (iii). Minerals 2019, 9, 430 6 of 47 Minerals 2019, 9, x FOR PEER REVIEW 6 of 45

(a) (b)

Bou Gn Ow Frs Dia Prg Frs Aef Gn Dia Dia Bou Gn Frs Gn Aef Gn

100  m 200  m

Frs Mia Ow Frg Dia Aef Mia Jms Mia Dia

200  m Mia 100  m

(e) (f) Prg

Ste Mia

Dia Gn Aef Frg

Frs Dia Aef Mia Dia Frg Mia Ste Mia 100  m 1000  m

Figure 2. (a) Black ore (i) association (from the earliest to the latest mineral): galena (Gn), boulangerite (Bou),Figure freieslebenite 2. (a) Black (Frs), ore (i) diaphorite association (Dia), (from pyrargyrite the earliest (Prg); to ( b the) example latest ofmineral): black ore galena (i) association (Gn), withboulangerite the general (Bo successionu), freieslebenite from the(Frs), Pb-richest diaphorite to Pb-poorer(Dia), pyrargyrite phases: (Prg); galena (b (Gn)) example –boulangerite of black (Bou)ore – freieslebenite(i) association (Frs) with – the owyheeite general (Ow)succession – fizélyite from (Fiz) the –Pb Ag-excess-richest to fiz Pbélyite-poorer (Aef) phases: – diaphorite galena (Dia);(Gn) – (c) a later-stageboulangerite replacement (Bou) – freieslebenite of galena of (Frs) black – oreowyheeite (i) by Ag-richer (Ow) – fizélyite minerals (Fiz) following – Ag-excess the succession: fizélyite (Aef) galena (white)– diaphorite – freieslebenite (Dia); (c) (Frs)a later –- diaphoritestage replacement (Dia) – freibergite of galena (Frg) of black –miargyrite ore (i) by (Mia) Ag- –richer jamesonite minerals (Jms); (followingd) needles the of owyheeitesuccession: (Ow)galena replaced (white) by– freieslebenite diaphorite (Dia) (Frs) and – diaphorite Ag-excess (Dia) fizé lyite– freibergite (Aef); all (Frg) minerals – aremiargyrite subsequently (Mia) – beingjamesonite replaced (Jms); by (d miargyrite) needles of (Mia);owyheeite (e) (Ow) five Ag-minerals replaced by diaphorite in one image: (Dia) and galena (Gn)Ag-excess replaced fizélyite by freislebenite (Aef); all minerals (Frs), diaphoriteare subsequently (Dia) andbeing Ag-excess replaced by fiz émiargyritelyite (Aef), (Mia); all replaced (e) five by miargyriteAg-minerals (Mia). in one Stephanite image: galena (Ste) (Gn) is the replaced latest mineral.by freislebenite (f) typical (Frs), example diaphorite of ore (Dia) (iii) and with Ag prevailing-excess miargyritefizélyite (Aef), (Mia) all in replaced quartz gangue, by miargyrite remnants (Mia). of galena Stephanite (white) (Ste) are isreplaced the latest by diaphorite mineral. (f (Dia)) typical which example of ore (iii) with prevailing miargyrite (Mia) in quartz gangue, remnants of galena (white) are is subsequently replaced by miargyrite, locally with pyraragyrite inclusions (Prg); freibergite (Frg) is also present. All back-scattered electron images.

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Table 1. EPMA data for diaphorite.

wt.% apfu Σ16 Atoms Analyses Ag Pb Sb As Se S Total Ag Pb Sb As Se S 477 24.21 29.15 26.95 0.05 0.27 18.86 99.48 3.04 1.91 3.00 0.01 0.05 7.97 1107 23.63 28.95 27.22 0.09 0.42 18.73 99.03 2.98 1.90 3.05 0.02 0.07 7.96 1106 23.96 28.74 27.60 0.03 0.45 18.55 99.33 3.03 1.89 3.09 0.01 0.08 7.89 1733 23.84 28.99 27.36 0.18 0.46 18.49 99.32 3.02 1.91 3.07 0.03 0.08 7.87 1850 23.43 29.41 27.34 0.15 0.53 18.75 99.60 2.95 1.93 3.05 0.03 0.09 7.93 727 24.01 28.87 27.02 0.10 0.56 18.82 99.38 3.01 1.89 3.01 0.02 0.10 7.95 1660 24.23 29.38 27.55 0.17 0.65 18.59 100.56 3.03 1.91 3.06 0.03 0.11 7.83 1223 24.31 28.52 27.23 0.09 0.99 18.47 99.61 3.05 1.86 3.03 0.02 0.17 7.80 2116 23.53 29.30 27.21 0.00 1.08 18.37 99.49 2.98 1.93 3.05 0.00 0.19 7.83 1886 24.24 29.53 27.49 0.00 1.29 18.71 101.25 3.01 1.91 3.02 0.01 0.22 7.82 799 24.08 29.20 27.61 0.06 1.64 18.37 100.97 3.01 1.90 3.06 0.01 0.28 7.72 800 24.42 29.31 27.83 0.05 1.71 18.44 101.76 3.03 1.89 3.06 0.01 0.29 7.69 Analyses are ordered according to increasing Se content.

Chemical composition of freieslebenite is relatively uniform and close to ideal formula (Table2); traces of As were identiﬁed. The anion part features contents of Se (up to 0.05 apfu, i.e., 0.71 wt.%). The SeS 1 substitution in freieslebenite is the least pronounced of all Ag-Pb-Sb sulfosalts, the maximum − determined contents of Se are only 0.71 wt.% compared to 1.71 wt.% in diaphorite and 4.69 wt.% in Ag-excess ﬁzélyite. The empirical formula for studied freieslebenite on the basis of 6 apfu (mean of 138 analyses) can be expressed as Ag0.99(Pb0.98Fe0.01)Σ0.99Sb1.02(S2.97Se0.02)Σ2.99.

Table 2. EPMA data for freieslebenite.

wt.% apfu Σ6 Atoms Analyses Ag Pb Sb As Se S Total Ag Pb Sb As Se S 569 20.50 37.96 23.61 0.08 0.28 18.39 100.82 0.99 0.96 1.01 0.01 0.02 3.00 1737 20.17 38.44 23.19 0.13 0.38 17.99 100.30 0.99 0.98 1.01 0.01 0.03 2.97 1861 20.14 38.57 23.33 0.15 0.40 18.21 100.80 0.98 0.98 1.01 0.01 0.03 2.99 1205 20.18 38.14 23.31 0.09 0.41 17.91 100.03 0.99 0.98 1.02 0.01 0.03 2.97 610 20.59 37.90 23.27 0.06 0.42 17.90 100.14 1.01 0.97 1.01 0.00 0.03 2.96 429 20.37 38.21 23.06 0.12 0.44 18.03 100.24 1.00 0.97 1.00 0.01 0.03 2.97 713 20.37 38.41 23.14 0.06 0.45 17.98 100.41 1.00 0.98 1.00 0.00 0.03 2.96 430 20.50 37.94 22.89 0.16 0.55 17.89 99.93 1.01 0.97 1.00 0.01 0.04 2.96 2149 20.13 37.90 23.15 0.00 0.66 17.83 99.67 0.99 0.97 1.01 0.00 0.04 2.96 2152 20.33 37.75 22.89 0.00 0.71 17.49 99.17 1.01 0.98 1.01 0.00 0.05 2.93 Analyses are ordered according to increasing Se content.

4.2.3. Ag-excess ﬁzélyite Ag6Pb14Sb21S48 Ag-excess ﬁzélyite (AEF) is by far the most abundant of all andorite minerals (ca. 770 analytical points compared to ca. 100 points of all other andorite minerals put together—Figure3). It is fairly frequent among microprobe analyses in polished sections. It occurs as anhedral grains, occasionally as semi-euhedral or column-like aggregates, usually up to 100 µm, in exceptional casesup to 1500 µm (Figure4), in black ore (i), most frequently associated with galena, boulangerite, jamesonite, owyheeite, other andorite group minerals and miargyrite (Figure2b,d,e, Figure5a–d). AEF usually replaces andorite IV, itself being replaced by freibergite and miargyrite. Minerals 2019, 9, x FOR PEER REVIEW 8 of 45

Table 2. EPMA data for freieslebenite.

wt.% apfu Ʃ6 Atoms Analyses Ag Pb Sb As Se S Total Ag Pb Sb As Se S 569 20.50 37.96 23.61 0.08 0.28 18.39 100.82 0.99 0.96 1.01 0.01 0.02 3.00 1737 20.17 38.44 23.19 0.13 0.38 17.99 100.30 0.99 0.98 1.01 0.01 0.03 2.97 1861 20.14 38.57 23.33 0.15 0.40 18.21 100.80 0.98 0.98 1.01 0.01 0.03 2.99 1205 20.18 38.14 23.31 0.09 0.41 17.91 100.03 0.99 0.98 1.02 0.01 0.03 2.97 610 20.59 37.90 23.27 0.06 0.42 17.90 100.14 1.01 0.97 1.01 0.00 0.03 2.96 429 20.37 38.21 23.06 0.12 0.44 18.03 100.24 1.00 0.97 1.00 0.01 0.03 2.97 713 20.37 38.41 23.14 0.06 0.45 17.98 100.41 1.00 0.98 1.00 0.00 0.03 2.96 430 20.50 37.94 22.89 0.16 0.55 17.89 99.93 1.01 0.97 1.00 0.01 0.04 2.96 2149 20.13 37.90 23.15 0.00 0.66 17.83 99.67 0.99 0.97 1.01 0.00 0.04 2.96 2152 20.33 37.75 22.89 0.00 0.71 17.49 99.17 1.01 0.98 1.01 0.00 0.05 2.93 Analyses are ordered according to increasing Se content.

4.2.3. Ag-excess fizélyite Ag6Pb14Sb21S48 Ag-excess fizélyite (AEF) is by far the most abundant of all andorite minerals (ca. 770 analytical points compared to ca. 100 points of all other andorite minerals put together—Figure 3). It is fairly frequent among microprobe analyses in polished sections. It occurs as anhedral grains, occasionally as semi-euhedral or column-like aggregates, usually up to 100 μm, in exceptional casesup to 1500 μm (Figure 4), in black ore (i), most frequently associated with galena, boulangerite, jamesonite, owyheeite, other andorite group minerals and miargyrite (Figures 2b,d,e, 5a–d). AEF usually replaces andorite IV, itself being replaced by freibergite and miargyrite. Minerals 2019, 9, 430 8 of 47

Minerals 2019, 9, x FOR PEER REVIEW 9 of 45

Ag-excess fizélyite was described for the first time on the basis of chemical analyses as “minéral F” from Les Farges (France) by Moëlo et al. [41] and later from the Lill mine in Příbram (Czech Republic) by Plášil et al. [42]. Structurally, it was defined by Yang et al. [43] in samples from Van Silver mine, Canada. It significantly differs from fizélyite in its higher Ag content. The excess silver is situated at the Ag2 site in the structure [43], which remains unoccupied in “normal” fizélyite. Higher Ag contents result in a shift of calculated Nchem (the width of the blocks of octahedra separated by Pb atoms in trigonal prismatic coordination) to higher values above 4. The mineral from Van Silver mine [43] shows calculated values of Nchem in the range of 4.31–4.59, mean 4.42. AEF from the Anthony of Padua Mine (Table 3) shows a wider range of Nchem values of 4.27–4.91, mean 4.54 (Figure 4). The determined range of the andorite substitution (Ag + Sb = 2Pb) varies between 57.6 and 67.4% (mean 63.7). Apart from sulphur, the anion contains significant selenium content up to 4.48 apfu (4.69 wt.%) (Figure 6), which is considerably higher than in all other andorite group minerals. The empirical formula for studied Ag-excess fizélyite on the basis of 88 apfu (mean of 767 analyses) can be expressed as

(Ag5.91Cu0.03Figure)Σ5.94Figure(Pb 3. Graph13.91 3. FeGraph0.15 NMnchem Nchem0.06value) Σ14.12value(Sb vs%and vs20.57%andAs substitution0.07substitution)Σ20.64(S47.68 (L%) (L%)Se0.53 for) forΣ48.21 andorite andorite. group group minerals minerals..

Aef Frs Aef Aef

Aef

500  m

FigureFigure 4. An4. A exceptionallyn exceptionally large large graingrain ofof Se-richSe-rich Ag Ag-excess-excess fizélyite ﬁzélyite (A (Aef),ef), 1500 1500 μmµ macross, across, with with a a variablevariable Se Secontent content (0.31–1.23 (0.31–1.23 wt.% wt.%of of Se). Se). Ag-excessAg-excess fizélyite ﬁzélyite replaces replaces earliest earliest galena galena (Gn (Gn)) and and is is replacedreplaced by by freieslebenite freieslebenite (Frs). (Frs).

Minerals 2019, 9, 430 9 of 47 Minerals 2019, 9, x FOR PEER REVIEW 10 of 45

(a) (b) Aef Aef

Ad4

Aef Ad4 Ad4 Aef Frs Ad6 Aef Aef 200  m 100  m

Ow Bou Gn Aef Aef Ow Gn Gn Aef Ow Dia

Ow Aef 200  m 100  m

Figure 5. (a) Andorite IV (Ad4) replaces Ag-excess fizélyite (Aef); (b) grain of Ag-excess fizélyite (Aef) inFigure kutnohorite 5. (a) Andorite of black IV ore (A (i)d4) is replaces replaced Ag by-excess andorite fizélyite IV (Ad4), (Aef); which (b) grain is subsequently of Ag-excess replaced fizélyite by andorite(Aef) in kutnohorite VI (Ad6; ragged of black edges). ore ( Ag-excessi) is replaced fiz ébylyite andorite is further IV (Ad4) replaced, which by freieslebenite is subsequently (Frs; replaced right side ofby the andorite grain); VI ( c(Ad6;) galena ragged (Gn) edges). replaced Ag by-excess boulangerite fizélyite is (Bou) further and replaced owyheeite by freieslebenite (Ow), both minerals (Frs; subsequentlyright side of the replaced grain); by (c Ag-excess) galena (G fizné) lyitereplaced (Aef);( byd )boulangerite earliest galena (Bou (Gn)) and replaced owyheeite by owyheeite (Ow), both (Ow), Ag-excessminerals subsequently fizélyite (Aef) replaced and diaphorite by Ag-excess (Dia). All fizélyite back-scattered (Aef);(d) earliest electron galena images. (Gn) replaced by owyheeite (Ow), Ag-excess fizélyite (Aef) and diaphorite (Dia). All back-scattered electron images. Ag-excess fizélyite was described for the first time on the basis of chemical analyses as “minéral F” from Les Farges (France) by MoëloTable 3. et EPMA al. [41 data] and for later of Ag from-excess the fizélyite. Lill mine in Pˇríbram (Czech Republic) wt.% apfu Ʃ88 Atoms byAnalyses Plášil et al. [42]. Structurally, it was defined by Yang et al. [43] in samples from Van Silver mine, Ag Pb Fe Cd Mn Sb Se S Total Ag Pb Fe Cd Mn Sb Se S N L% Canada.1868 7.86 It significantly37.19 0.49 0.00 di ff0.12ers 33.51 from 0.06 fiz é20.70lyite 100.12 in its higher5.39 13.29 Ag 0.65 content. 0.00 0.16 The 20.38 excess 0.05 silver47.80 4.29 is situated62.36 at1496 the Ag28.63site 37.28 in the0.10 structure0.00 0.05 33.12 [43 ],0.28 which 20.22 remains99.86 6.01 unoccupied 13.51 0.13 0.00 in “normal”0.07 20.43 fiz0.27é lyite.47.35 4.50 Higher 65.88 Ag contents767 8.37 result 37.46 in a0.14 shift 0.21 of 0.05 calculated 32.74 0.35 N 20.24 (the99.67 width5.82 13.56 of the 0.19 blocks 0.14 0.06 of octahedra20.16 0.33 separated47.34 4.58 62.68 by Pb 1392 7.84 38.31 0.13 0.00 0.20 32.23 0.46 chem20.07 99.36 5.50 13.99 0.17 0.00 0.27 20.03 0.44 47.35 4.54 60.74 atoms1955 in8.20 trigonal 37.20 0.11 prismatic 0.00 0.05 coordination) 33.77 0.70 20.24 to 100.33 higher 5.68 values 13.42 above0.15 0.00 4. 0.07 The 20.73 mineral 0.66 47.18 from 4.31 Van 65.29 Silver mine594 [43]8.51 shows 35.97 calculated 0.46 0.02 values0.14 34.03 of N0.75 20.13in the100.10 range 5.86 of12.89 4.31–4.59, 0.62 0.01 mean 0.19 4.42.20.76 AEF0.71 from46.60 the4.45 Anthony64.55 647 8.79 38.52 0.08 0.00 0.04 32.45 0.85chem 20.07 100.86 6.10 13.93 0.11 0.00 0.05 19.97 0.80 46.88 4.83 63.19 of1920 Padua 7.99 Mine 37.65 (Table 0.71 30.00) shows 0.03 32.84 a wider 0.96 19.79 range 100.03 of N5.57chem 13.67values 0.95 of0.004.27–4.91, 0.05 20.29 mean0.91 46.43 4.54 4.50 (Figure 60.53 4). The781 determined 8.52 36.31 range 0.21 of0.00 the 0.06 andorite 33.38 1.26 substitution 20.01 99.84 (Ag 5.91+ Sb13.11= 2Pb) 0.29 varies0.00 0.09 between 20.52 57.61.19 and46.71 67.4%4.49 65.84 (mean 641 8.29 37.58 0.11 0.00 0.04 32.86 1.66 19.65 100.19 5.80 13.70 0.14 0.00 0.06 20.39 1.59 46.29 4.50 63.74 63.7).783 Apart8.86 from36.07 sulphur,0.19 0.00 the0.05 anion33.39 1.87 contains 19.70 significant100.33 6.14 13.02 selenium 0.25 0.00 content 0.07 up20.51to 1.77 4.48 45.95apfu 4.63(4.69 67.05 wt.%) (Figure784 6),8.76 which 36.52 is0.11 considerably 0.00 0.05 33.03 higher 2.05 19.57 than 100.31 in all 6.09 other 13.23 andorite 0.15 0.00 group 0.07 20.37 minerals. 1.95 45.82 The 4.70 empirical 66.34 1148 8.71 36.68 0.05 0.00 0.02 31.99 2.86 19.14 99.47 6.14 13.47 0.06 0.00 0.03 19.99 2.75 45.42 4.73 64.83 formula1144 for8.72 studied36.93 0.02 Ag-excess 0.00 0.00 fiz32.71élyite 3.50 on 18.84 the basis100.75 of6.13 88 13.50apfu (mean0.03 0.00 of 0.00 767 analyses)20.35 3.36 can44.51 be4.64 expressed 65.70 as1145 (Ag 8.82Cu 36.93) 0.03(Pb 0.00 0.00Fe 32.61Mn 3.49 )18.63 (Sb100.53 6.23As 13.58) 0.03 (S0.00 0.00Se 20.41) 3.37. 44.27 4.70 65.69 1143 5.919.07 0.0337.30Σ 5.940.02 0.0013.91 0.01 0.1533.11 4.690.06 Σ18.6314.12 102.9120.57 6.28 0.0713.43 Σ20.640.03 0.0047.68 0.01 0.5320.29Σ 48.214.43 43.34 4.73 65.98 Analyses are ordered according to increasing Se content.

Minerals 2019, 9, 430 10 of 47

4.2.4. Fizélyite Ag5Pb14Sb21S48 Fizélyite occurs only rarely in polished section (determined in only seven samples) as euhedral grains of tabular shape with hypoparallel intergrowth. It occurs as inclusions of up to 50 µm in jamesonite enclosed in boulangerite which replaces galena. It also occurs as individual grains in quartz up to 100 µm associated with jamesonite and miargyrite. It is also associated with owyheeite, boulangerite, other andorite minerals and diaphorite (Figure2a). It is found only in black ore (i), as with all andorite group minerals. The classification of fizélyite and Ag-excess fizélyite comes from the following assumptions. The formula of fizélyite is Ag5Pb14Sb21S48, which gives N = 4.00 and L% = 62.49. The formula of Ag-excess fizélyite is Ag6Pb14Sb21S48, which corresponds to N = 4.46 and L% = 64.85. Considering that AEF defines one more Ag atom compared to fizélyite [43], the borderline between fizélyite and Ag-excess fizélyite must be guided by the content of 0.5 Ag atom more against fizélyite, i.e., by the formula Ag5.5Pb14Sb21S48, which yields the values of N = 4.22 and L% = 63.76. Chemical composition of fizélyite and corresponding chemical formulae are given in Table4. In comparison with Ag-excess fizélyite (Figure3), the determined range of N chem values is centred around an ideal N value equal to 4 and ranges from 3.90 to 4.19 (mean 4.09). Determined values of the Ag + Sb = 2Pb substitution between 57.7 and 62.2% are slightly lower than 62.5 published for ideal fizélyite [41,43]. Found contents of Se do not exceed 1.17 apfu (1.20 wt.%) (Figure6) and are significantly lower than those found in Ag-excess fizélyite. Another difference against AEF is the presence of minor elements, namely iron. All fizélyite analyses show increased Fe betweenMinerals 2019 0.38, 9, x and FOR 0.94PEER wt.%,REVIEW mean 0.59, while the same value for AEF is 0.20. The empirical11 of 45 formula for studied fizélyite on the basis of 88 apfu (mean of 9 analyses) can be expressed as (Ag4.83Cu0.02)Σ4.85(Pb13.58Fe0.83Mn0.06Cd0.03)Σ14.50(Sb20.61As0.04)Σ20.65(S47.53Se0.40)Σ47.93.

FigureFigure 6. 6.Graph Graph SeSe/(S/(S + + Se)Se) vsvs AgAg (at.%)(at.%) forfor andoriteandorite groupgroup minerals.minerals.

4.2.4. Fizélyite Ag5Pb14Sb21S48 Fizélyite occurs only rarely in polished section (determined in only seven samples) as euhedral grains of tabular shape with hypoparallel intergrowth. It occurs as inclusions of up to 50 μm in jamesonite enclosed in boulangerite which replaces galena. It also occurs as individual grains in quartz up to 100 μm associated with jamesonite and miargyrite. It is also associated with owyheeite, boulangerite, other andorite minerals and diaphorite (Figure 2a). It is found only in black ore (i), as with all andorite group minerals. The classification of fizélyite and Ag-excess fizélyite comes from the following assumptions. The formula of fizélyite is Ag5Pb14Sb21S48, which gives N = 4.00 and L% = 62.49. The formula of Ag-excess fizélyite is Ag6Pb14Sb21S48, which corresponds to N = 4.46 and L% = 64.85. Considering that AEF defines one more Ag atom compared to fizélyite [43], the borderline between fizélyite and Ag-excess fizélyite must be guided by the content of 0.5 Ag atom more against fizélyite, i.e., by the formula Ag5.5Pb14Sb21S48, which yields the values of N = 4.22 and L% = 63.76. Chemical composition of fizélyite and corresponding chemical formulae are given in Table 4. In comparison with Ag-excess fizélyite (Figure 3), the determined range of Nchem values is centred around an ideal N value equal to 4 and ranges from 3.90 to 4.19 (mean 4.09). Determined values of the Ag + Sb = 2Pb substitution between 57.7 and 62.2% are slightly lower than 62.5 published for ideal fizélyite [41,43]. Found contents of Se do not exceed 1.17 apfu (1.20 wt.%) (Figure 6) and are significantly lower than those found in Ag-excess fizélyite. Another difference against AEF is the presence of minor elements, namely iron. All fizélyite analyses show increased Fe between 0.38 and 0.94 wt.%, mean 0.59, while the same value for AEF is 0.20. The empirical formula for studied fizélyite on the basis of 88 apfu (mean of 9 analyses) can be expressed as (Ag4.83Cu0.02)Σ4.85(Pb13.58Fe0.83Mn0.06Cd0.03)Σ14.50(Sb20.61As0.04)Σ20.65(S47.53Se0.40)Σ47.93.

Minerals 2019, 9, 430 11 of 47

Table 3. EPMA data for of Ag-excess ﬁzélyite.

wt.% apfu Σ88 Atoms Analyses Ag Pb Fe Cd Mn Sb Se S Total Ag Pb Fe Cd Mn Sb Se S N L% 1868 7.86 37.19 0.49 0.00 0.12 33.51 0.06 20.70 100.12 5.39 13.29 0.65 0.00 0.16 20.38 0.05 47.80 4.29 62.36 1496 8.63 37.28 0.10 0.00 0.05 33.12 0.28 20.22 99.86 6.01 13.51 0.13 0.00 0.07 20.43 0.27 47.35 4.50 65.88 767 8.37 37.46 0.14 0.21 0.05 32.74 0.35 20.24 99.67 5.82 13.56 0.19 0.14 0.06 20.16 0.33 47.34 4.58 62.68 1392 7.84 38.31 0.13 0.00 0.20 32.23 0.46 20.07 99.36 5.50 13.99 0.17 0.00 0.27 20.03 0.44 47.35 4.54 60.74 1955 8.20 37.20 0.11 0.00 0.05 33.77 0.70 20.24 100.33 5.68 13.42 0.15 0.00 0.07 20.73 0.66 47.18 4.31 65.29 594 8.51 35.97 0.46 0.02 0.14 34.03 0.75 20.13 100.10 5.86 12.89 0.62 0.01 0.19 20.76 0.71 46.60 4.45 64.55 647 8.79 38.52 0.08 0.00 0.04 32.45 0.85 20.07 100.86 6.10 13.93 0.11 0.00 0.05 19.97 0.80 46.88 4.83 63.19 1920 7.99 37.65 0.71 0.00 0.03 32.84 0.96 19.79 100.03 5.57 13.67 0.95 0.00 0.05 20.29 0.91 46.43 4.50 60.53 781 8.52 36.31 0.21 0.00 0.06 33.38 1.26 20.01 99.84 5.91 13.11 0.29 0.00 0.09 20.52 1.19 46.71 4.49 65.84 641 8.29 37.58 0.11 0.00 0.04 32.86 1.66 19.65 100.19 5.80 13.70 0.14 0.00 0.06 20.39 1.59 46.29 4.50 63.74 783 8.86 36.07 0.19 0.00 0.05 33.39 1.87 19.70 100.33 6.14 13.02 0.25 0.00 0.07 20.51 1.77 45.95 4.63 67.05 784 8.76 36.52 0.11 0.00 0.05 33.03 2.05 19.57 100.31 6.09 13.23 0.15 0.00 0.07 20.37 1.95 45.82 4.70 66.34 1148 8.71 36.68 0.05 0.00 0.02 31.99 2.86 19.14 99.47 6.14 13.47 0.06 0.00 0.03 19.99 2.75 45.42 4.73 64.83 1144 8.72 36.93 0.02 0.00 0.00 32.71 3.50 18.84 100.75 6.13 13.50 0.03 0.00 0.00 20.35 3.36 44.51 4.64 65.70 1145 8.82 36.93 0.03 0.00 0.00 32.61 3.49 18.63 100.53 6.23 13.58 0.03 0.00 0.00 20.41 3.37 44.27 4.70 65.69 1143 9.07 37.30 0.02 0.00 0.01 33.11 4.69 18.63 102.91 6.28 13.43 0.03 0.00 0.01 20.29 4.43 43.34 4.73 65.98 Analyses are ordered according to increasing Se content.

Table 4. EPMA data for ﬁzélyite.

wt.% apfu Σ88 Atoms Analyses Ag Pb Fe Cd Mn Sb Se S Total Ag Pb Fe Cd Mn Sb Se S N L% 556 6.90 37.65 0.65 0.36 0.07 33.84 0.21 20.84 100.57 4.72 13.39 0.86 0.24 0.09 20.49 0.20 47.91 4.05 58.51 479 6.98 37.56 0.53 0.04 0.07 33.30 0.23 19.93 98.62 4.93 13.80 0.72 0.02 0.10 20.83 0.23 47.32 4.08 59.54 1172 7.46 37.95 0.38 0.00 0.09 33.92 0.25 20.63 100.74 5.12 13.57 0.50 0.00 0.12 20.64 0.24 47.68 4.15 61.58 729 6.71 37.18 0.94 0.01 0.06 33.33 0.32 20.42 99.03 4.65 13.43 1.26 0.01 0.08 20.49 0.30 47.65 4.02 58.00 1903 7.43 37.71 0.45 0.00 0.01 34.19 0.72 20.44 101.05 5.10 13.48 0.60 0.00 0.02 20.79 0.68 47.19 4.10 62.23 2062 7.11 36.56 0.57 0.00 0.03 33.33 1.20 19.25 98.06 5.07 13.58 0.79 0.00 0.04 21.07 1.17 46.22 4.06 61.44 Analyses are ordered according to increasing Se content. Minerals 2019, 9, 430 12 of 47

4.2.5. Andorite IV Ag15Pb18Sb47S96 Andorite IV is the second most frequent andorite mineral (10 samples, 70 point analyses). It is most often found as grains and inclusions up to 300 µm in Ag-excess ﬁzélyite which is replaced by andorite IV, and also as worm-like relict aggregates associated with andorite VI, occasionally mutually intergrowing, associated with boulangerite, owyheeite, jamesonite, freieslebenite and diaphorite in black ore (i) (Figure5a,b). Andorite IV is sometimes as lamellae as much as 150 µm long and 30 µm wide. According to the degree of replacement, only amoebic relics, frayed or ragged at the edges, remain. The earliest mineral in the association is galena, followed by andorite IV, which is replaced by andorite VI, which are corroded by owyheeite and ﬁzélyite. Thus, this is an opposite trend to the general succession. Chemical analyses of andorite IV (Table5, Figure3) revealed N chem values between 3.88 and 4.09 Minerals(mean 2019 3.96), 9, and x FOR L% PEER (percentage REVIEW of the andorite 2Pb = Ag + Sb substitution) between 90.21 and13 97.21of 45 (mean 94.18), which is in a good agreement with published data of this mineral phase [41]. The SeS 1 − substitution does not exceed 3.24Tableapfu (1.76 6. EPMA wt.% data Se) for (Figure andorite6). VI.

wt.% apfu Ʃ11 Atoms Analyses4.2.6. Andorite VI, AgPbSb S Ag Pb Fe Sb3 6 As Se S Total Ag Pb Fe Sb As Se S N L% 1273Andorite 11.75 VI24.02 is much0.07 41.89 less frequent0.08 0.14than 22.08 andorite 100.02 IV0.95 (17 1.01 point 0.01 analyses 3.00 0.01 of four0.02 samples).6.00 3.86 It100.07 was found1300 in black11.84 ore23.07 (i) 0.09 as anhedral 41.32 0.05 grains 0.21 up 22.12 to 80 µ98.70m in earlier0.96 0.98 Ag-excess 0.01 2.97 ﬁz é0.01lyite, 0.02 which 6.04 is replaced3.90 100.67 by 2075 11.99 23.36 0.07 41.56 0.00 0.22 21.27 98.47 0.99 1.01 0.01 3.04 0.00 0.02 5.91 3.92 100.50 andorite1299 IV,12.11 which 23.64 is then0.06 replaced42.03 0.07 by 0.23 andorite 22.10 VI,100.22 and, 0.97 occassionally, 0.99 0.01 as3.00 anhedral 0.01 0.02 grains 5.98 up 3.93 to 250100.36µm in2076 earlier 11.88 Ag-excess 23.15 ﬁz0.06élyite 41.68 with 0.00 all or0.24 most 21.42 of andorite98.43 0.98 IV being0.99 0.01 replaced 3.04 by0.00 andorite 0.03 5.94 VI (Figure3.87 101.525b). It1291 is the mineral11.89 23.48 with 0.10 the highest41.88 0.02 andorite 0.26 substitution22.12 99.75 (2Pb0.96 =0.99Ag 0.0+ Sb),2 2.99 i.e. 0.00 the lowest0.03 6.00 Pb and3.89 highest100.69 Ag1769 and Sb11.95 contents, 24.51 and0.08 it41.89 appears 0.15 as0.32 the latest21.93 mineral100.83 0.96 in the1.03 association 0.01 2.99 of0.02 andorite 0.03 5.94 group 3.91 minerals. 98.87 1745 12.08 23.78 0.07 41.83 0.17 0.34 21.83 100.09 0.98 1.00 0.01 3.00 0.02 0.04 5.94 3.92 100.30 2065Chemical 12.03 composition23.45 0.07 41.67 of andorite0.00 0.88 VI 20.97 and corresponding99.07 0.99 1.01 chemical 0.01 3.05 formulae 0.00 0.10 are given5.83 3.93 in Table100.426 . N2164chem values11.91 3.80–4.0223.25 0.05 (mean 41.53 3.91) 0.00 and 0.94 the 21.02 andorite 98.70 substitution 0.98 1.00 percentage0.01 3.04 0.00 (L%) 0.11 97.4–102.2 5.84 3.90 (Figure 100.863) correspond2166 11.80 to the23.69 published 0.07 40.92 data 0.00 of this1.31 mineral 20.47 [98.2641]. The0.99 Se 1.03 for S0.01 substitution 3.04 0.00 is similar0.15 5.77 to andorite3.95 98.91 IV and does not exceed 0.15Analysesapfu (1.31 are wt.%) ordered (Figure according6). to increasing Se content.

4.2.7.4.2.7. Owyheeite Owyheeite,, Ag Ag3Pb3Pb1010SbSb11S1128S 28 OwyheeiteOwyheeite occurs occurs as massive needle-likeneedle-like steel steel to to lead lead grey grey aggregates aggregates up up to to 2 cm 2 cm long long inquartz in quartz and andkutnohorite kutnohorite associated associated or intergrowing or intergrowing with massive with massive boulangerite, boulangerite, miargyrite miargyrite and pyrite. and It pyrite occurs. It in occursblack ore in (i)black associated ore (i) with associated galena, Pb-Sb with sulfosalts galena, Pb (boulangerite,-Sb sulfosalts jamesonite) (boulangerite, and Ag-Pb-Sb jamesonite) sulfosalts and Ag(andorite-Pb-Sb group sulfosalts minerals, (andorite freieslebenite group minerals, and diaphorite) freieslebenite (Figure5 c,d). and Itdiaphorite) is frequent ( inFigure polished 5c,d) sections. It is frequent(160 point in analyses).polished se Itctions was found (160 point as elongated analyses). lamellae It was found up to 100as elongatedµm in length lamellae and 20 upµ mto in100 width μm informing length massiveand 20 μm grains in width several forming hundred massive microns grains across. several hundred microns across. TheThe chemical chemical composition composition of of owyheeite owyheeite (Table (Table 7 7)) is is close close to to ideal ideal formula formula Ag Ag3Pb3Pb1010SbSb1111SS2828 proposproposeded by by Moëlo Moëlo et et al. al. [ [4444],], with with a a slight slight deficit deﬁcit of of Pb Pb and and an an excess excess of of Sb. Sb. Figure Figure 7 shows that contentscontents of of main main elements elements Ag, Ag, Pb Pb and and Sb do not correlate correlate signiﬁcantly significantly and and the the 2Pb 2Pb↔AgAg ++ SbSb substitutionsubstitution presented presented by by Mo Moëloëlo et et al. al. [ [4545]] is is not not the the dominant dominant factor factor in in the the chemical chemical composition composition of of owyheeite.owyheeite. The The determined determined contents contents of of selenium selenium in in the the studied studied mineral mineral are are relatively relatively low low (0.12 (0.12–1.17–1.17 apfuapfu; ; 0.21 0.21–1.97–1.97 wt.%). wt.%). Its Its average average composition composition (113 (113 analyses) analyses) is possible is possible to express to express by empirical by empirical formula formula (Ag2.96Cu0.03)Σ2.99(Pb9.63Fe0.02)Σ9.65(Sb11.18As0.03)Σ11.21(S27.73Se0.36Cl0.04)Σ28.13 on the basis of 52 apfu. (Ag2.96Cu0.03)Σ2.99(Pb9.63Fe0.02)Σ9.65(Sb11.18As0.03)Σ11.21(S27.73Se0.36Cl0.04)Σ28.13 on the basis of 52 apfu.

11.8 10.2 (a) (b) 11.6

10.0 )

) 11.4

f f p

p 9.8

a a

( (

11.2 e

A F

+ + b

b 9.6 P S 11.0

9.4 10.8

10.6 9.2 9.2 9.4 9.6 9.8 10.0 10.2 2.7 2.8 2.9 3.0 3.1 3.2 3.3

Pb+Fe (apfu) Ag+Cu (apfu)

Figure 7. Graph Ag + Cu vs Sb + As (apfu) (a) and Ag + Cu vs Pb + Fe (apfu) (b) for owyheeite.

Minerals 2019, 9, 430 13 of 47

Table 5. EPMA data for andorite IV.

wt.% apfu Σ88 Atoms Analyses Ag Pb Fe Sb As Se S Total Ag Pb Fe Sb As Se S N L% 947 11.28 25.41 0.13 40.50 0.00 0.22 21.77 99.31 3.69 4.33 0.08 11.75 0.01 0.10 23.97 3.95 94.65 1160 11.54 25.95 0.19 40.72 0.07 0.30 22.03 100.79 3.72 4.36 0.12 11.64 0.03 0.13 23.92 4.02 93.28 1899 11.29 26.58 0.16 40.80 0.08 0.36 21.62 100.87 3.68 4.51 0.10 11.77 0.04 0.16 23.69 3.96 92.96 953 10.99 25.94 0.06 40.02 0.00 0.37 21.34 98.71 3.65 4.48 0.04 11.76 0.02 0.17 23.81 3.93 93.79 1742 11.28 26.02 0.11 40.57 0.14 0.45 21.60 100.18 3.69 4.43 0.07 11.75 0.07 0.20 23.75 3.95 94.22 1743 11.21 26.06 0.12 40.06 0.17 0.45 21.45 99.52 3.69 4.47 0.08 11.68 0.08 0.20 23.75 3.97 93.31 950 11.16 25.48 0.12 40.40 0.06 0.46 21.47 99.14 3.68 4.37 0.07 11.79 0.03 0.21 23.79 3.92 94.78 1722 11.05 26.62 0.07 40.34 0.12 0.52 21.29 100.00 3.64 4.57 0.05 11.78 0.05 0.23 23.61 3.92 93.13 1586 11.07 27.03 0.14 39.41 0.17 0.61 20.99 99.42 3.69 4.69 0.09 11.62 0.08 0.28 23.51 4.01 91.59 1587 11.18 26.91 0.06 40.35 0.13 0.62 21.25 100.49 3.68 4.61 0.04 11.76 0.06 0.28 23.51 3.94 93.21 2146 11.44 25.55 0.12 39.72 0.00 0.90 20.92 98.65 3.81 4.44 0.08 11.73 0.00 0.41 23.47 4.07 92.95 2156 11.37 25.36 0.13 39.71 0.00 1.20 20.64 98.41 3.81 4.43 0.08 11.80 0.00 0.55 23.29 4.04 93.40 2155 11.46 25.34 0.10 39.71 0.00 1.76 20.26 98.63 3.86 4.44 0.07 11.84 0.00 0.81 22.95 4.07 93.54 Analyses are ordered according to increasing Se content.

Table 6. EPMA data for andorite VI.

wt.% apfu Σ11 Atoms Analyses Ag Pb Fe Sb As Se S Total Ag Pb Fe Sb As Se S N L% 1273 11.75 24.02 0.07 41.89 0.08 0.14 22.08 100.02 0.95 1.01 0.01 3.00 0.01 0.02 6.00 3.86 100.07 1300 11.84 23.07 0.09 41.32 0.05 0.21 22.12 98.70 0.96 0.98 0.01 2.97 0.01 0.02 6.04 3.90 100.67 2075 11.99 23.36 0.07 41.56 0.00 0.22 21.27 98.47 0.99 1.01 0.01 3.04 0.00 0.02 5.91 3.92 100.50 1299 12.11 23.64 0.06 42.03 0.07 0.23 22.10 100.22 0.97 0.99 0.01 3.00 0.01 0.02 5.98 3.93 100.36 2076 11.88 23.15 0.06 41.68 0.00 0.24 21.42 98.43 0.98 0.99 0.01 3.04 0.00 0.03 5.94 3.87 101.52 1291 11.89 23.48 0.10 41.88 0.02 0.26 22.12 99.75 0.96 0.99 0.02 2.99 0.00 0.03 6.00 3.89 100.69 1769 11.95 24.51 0.08 41.89 0.15 0.32 21.93 100.83 0.96 1.03 0.01 2.99 0.02 0.03 5.94 3.91 98.87 1745 12.08 23.78 0.07 41.83 0.17 0.34 21.83 100.09 0.98 1.00 0.01 3.00 0.02 0.04 5.94 3.92 100.30 2065 12.03 23.45 0.07 41.67 0.00 0.88 20.97 99.07 0.99 1.01 0.01 3.05 0.00 0.10 5.83 3.93 100.42 2164 11.91 23.25 0.05 41.53 0.00 0.94 21.02 98.70 0.98 1.00 0.01 3.04 0.00 0.11 5.84 3.90 100.86 2166 11.80 23.69 0.07 40.92 0.00 1.31 20.47 98.26 0.99 1.03 0.01 3.04 0.00 0.15 5.77 3.95 98.91 Analyses are ordered according to increasing Se content. Minerals 2019, 9, 430 14 of 47

Table 7. EPMA data for owyeeite.

wt.% apfu Σ52 Atoms Analyses Ag Pb Fe Sb As Se S Total Ag Cu Pb Fe Sb As Se S 822 6.70 44.08 0.09 28.90 0.00 0.21 19.34 99.32 2.88 0.03 9.86 0.08 11.00 0.03 0.12 27.95 1004 6.81 43.21 0.00 29.59 0.07 0.54 19.50 99.72 2.90 0.01 9.56 0.03 11.15 0.04 0.31 27.89 1193 6.87 43.79 0.05 29.42 0.00 1.14 19.45 100.72 2.90 0.02 9.63 0.04 11.01 0.02 0.66 27.65 1190 6.92 43.69 0.11 29.51 0.00 0.93 19.36 100.51 2.93 0.03 9.64 0.09 11.09 0.01 0.54 27.61 1195 6.98 44.06 0.00 29.80 0.07 0.96 19.45 101.32 2.94 0.02 9.67 0.02 11.13 0.04 0.55 27.58 1192 6.97 43.36 0.05 29.55 0.08 1.09 19.26 100.35 2.96 0.01 9.59 0.04 11.12 0.05 0.63 27.53 1191 6.98 43.51 0.00 29.50 0.06 1.04 19.30 100.38 2.96 0.01 9.62 0.03 11.10 0.04 0.60 27.58 1194 7.06 43.39 0.00 29.51 0.07 1.11 19.26 100.41 3.00 0.02 9.59 0.03 11.10 0.04 0.64 27.51 1188 7.10 43.64 0.08 29.76 0.00 0.97 19.31 100.87 3.01 0.02 9.62 0.07 11.16 0.02 0.56 27.50 712 7.19 43.18 0.26 29.58 0.07 0.93 19.29 100.51 3.04 0.03 9.52 0.21 11.09 0.04 0.54 27.47 1511 7.14 43.05 0.00 29.52 0.12 1.09 18.95 99.86 3.06 0.03 9.60 0.02 11.20 0.07 0.64 27.31 1698 7.23 44.14 0.00 28.86 0.16 0.42 19.40 100.20 3.08 0.06 9.78 0.01 10.89 0.10 0.24 27.79 1503 7.24 42.30 0.07 29.70 0.09 0.93 19.10 99.43 3.09 0.03 9.41 0.06 11.24 0.06 0.55 27.45 1512 7.24 42.51 0.00 29.69 0.19 1.63 18.79 100.03 3.10 0.01 9.47 0.00 11.26 0.12 0.95 27.05 2095 7.47 42.21 0.00 30.38 0.00 0.44 19.35 99.85 3.18 0.02 9.35 0.03 11.45 0.00 0.26 27.69 Analyses are ordered according to increasing Ag content. Minerals 2019, 9, x FOR PEER REVIEW 13 of 45

Table 6. EPMA data for andorite VI.

wt.% apfu Ʃ11 Atoms Analyses Ag Pb Fe Sb As Se S Total Ag Pb Fe Sb As Se S N L% 1273 11.75 24.02 0.07 41.89 0.08 0.14 22.08 100.02 0.95 1.01 0.01 3.00 0.01 0.02 6.00 3.86 100.07 1300 11.84 23.07 0.09 41.32 0.05 0.21 22.12 98.70 0.96 0.98 0.01 2.97 0.01 0.02 6.04 3.90 100.67 2075 11.99 23.36 0.07 41.56 0.00 0.22 21.27 98.47 0.99 1.01 0.01 3.04 0.00 0.02 5.91 3.92 100.50 1299 12.11 23.64 0.06 42.03 0.07 0.23 22.10 100.22 0.97 0.99 0.01 3.00 0.01 0.02 5.98 3.93 100.36 2076 11.88 23.15 0.06 41.68 0.00 0.24 21.42 98.43 0.98 0.99 0.01 3.04 0.00 0.03 5.94 3.87 101.52 1291 11.89 23.48 0.10 41.88 0.02 0.26 22.12 99.75 0.96 0.99 0.02 2.99 0.00 0.03 6.00 3.89 100.69 1769 11.95 24.51 0.08 41.89 0.15 0.32 21.93 100.83 0.96 1.03 0.01 2.99 0.02 0.03 5.94 3.91 98.87 1745 12.08 23.78 0.07 41.83 0.17 0.34 21.83 100.09 0.98 1.00 0.01 3.00 0.02 0.04 5.94 3.92 100.30 2065 12.03 23.45 0.07 41.67 0.00 0.88 20.97 99.07 0.99 1.01 0.01 3.05 0.00 0.10 5.83 3.93 100.42 2164 11.91 23.25 0.05 41.53 0.00 0.94 21.02 98.70 0.98 1.00 0.01 3.04 0.00 0.11 5.84 3.90 100.86 2166 11.80 23.69 0.07 40.92 0.00 1.31 20.47 98.26 0.99 1.03 0.01 3.04 0.00 0.15 5.77 3.95 98.91 Analyses are ordered according to increasing Se content.

11.8 10.2 (a) (b) 11.6

10.0 )

) 11.4

f f p

p 9.8

a a

( (

11.2 e

A F

+ + b

b 9.6 P S 11.0

9.4 10.8

10.6 9.2 9.2 9.4 9.6 9.8 10.0 10.2 2.7 2.8 2.9 3.0 3.1 3.2 3.3

Pb+Fe (apfu) Ag+Cu (apfu)

Figure 7. Graph Ag + Cu vs Sb + As (apfu)(a) and Ag + Cu vs Pb + Fe (apfu)(b) for owyheeite. Figure 7. Graph Ag + Cu vs Sb + As (apfu) (a) and Ag + Cu vs Pb + Fe (apfu) (b) for owyheeite. 4.2.8. Ag-Poor Ag-Pb-Sb Sulfosalts Ag-poor Ag-Pb-Sb sulfosalts are chemically similar to owyheeite, but show lower contents of Ag and higher contents of Pb. Most often it forms lamellae several tens of microns across enclosed in owyheeite or boulangerite, which it replaces (in agreement with the general succession) (Figure8). It is closely associated with owyheeite, boulangerite, galena, jamesonite and Ag-excess ﬁzélyite. It is much

Mineralsrarer than 2019 owyheeite, 9, x FOR PEER (21 REVIEW point analyses, compared to 160 analyses of owyheeite). 15 of 45

Gn Aef Bou Jms Aps

Jms

Gn Bou

30  m

Figure 8. GrainGrain of of Ag Ag-poor-poor Ag Ag-Pb-Sb-Pb-Sb sulfosalt sulfosalt (Ap (Aps,s, 3.3 3.3 wt wt.%.% Ag) Ag) in in boulangerite boulangerite (B (Bou)ou) in association with jamesonite (J (Jms),ms), Ag Ag-excess-excess f ﬁzizééllyiteyite (Aef)(Aef) and galena (Gn).(Gn). The The succession succession runs runs as as:: galena galena – – boulangerite – jamesonite – Ag-poorAg-poor Ag Ag-Pb-Sb-Pb-Sb sulfosalt – Ag-excessAg-excess ﬁzfizéélyite.lyite.

The Ag-poor part (with Ag contents lower than in the case of owyheeite) is an interestingand so far32 not a well-known part of theAg-Pb-Sb-S system,with24 only two approved minerals—questionable (a) Ag-poor Ag-Pb-Sb sulfosalts, this paper (b) zoubekite30 [45,46] and tubulite—with unusual tubular morphology and crystal structure [47]. owyheeite, this paper 22 M3

We28 identiﬁed mineralAg-poor phases Ag-Pb-Sb sulfosalts, with published 0.7–4.3 data at.% Ag (0.87–5.12 wt.% Ag), which can be divided ) into four groups of compositions (Table8) di ﬀering by) Agboulangerite content: a) four analyses withzoubekite 0.87–1.16 wt.%

% 26 boulangerite

% T

20 .

UM1979-14 .

t a

of Ag; b) nine analyses with 2.02–2.87 wt.% Ag; c)a four analyses with 3.31–4.29 wt.%; and d) four (

( M2

24 s

e T F analyses with 5.08–5.20 wt.%. The determinedUM1990-32 AgA and Pb contents show negative correlation with

+ 18

22 M2 + b

b UM1979-14 UM1990-32 P M3 zoubekite S 20 16 Ag-poor Ag-Pb-Sb sulfosalts, this paper owyheeite, this paper 18 Ag-poor Ag-Pb-Sb sulfosalts, published data 16 14 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 Ag+Cu (at. %) Ag+Cu (at. %) Figure 9.(a) Graph Ag + Cu vs Pb + Fe (at.%) for Ag-poor Ag-Pb-Sb sulfosalts and owyheeite; boulangerite ideal composition Pb5Sb4S11; T-tubulite ideal composition Ag2Pb22Sb20S53[47]; unnamed M3—Příbram [48]; unnamed M2—Příbram [48]; UM1979-14—Primorye [49,50]; UM1990-32; zoubekite ideal composition AgPb4Sb4S10 [46].(b) graph Ag + Cu vs. Sb + As (at.%) for Ag-poor Ag-Pb-Sb sulfosalts and owyheeite; boulangerite ideal composition Pb5Sb4S11; T-tubulite ideal

composition Ag2Pb22Sb20S53 [47]; unnamed M3—Příbram [48]; unnamed M2—Příbram [48]; UM1979-14—Primorye [49]; UM1990-32 [50]; zoubekite ideal composition AgPb4Sb4S10 [46].

Minerals 2019, 9, x FOR PEER REVIEW 13 of 45

Table 6. EPMA data for andorite VI.

4.2.7. Owyheeite, Ag3Pb10Sb11S28 Owyheeite occurs as massive needle-like steel to lead grey aggregates up to 2 cm long in quartz and kutnohorite associated or intergrowing with massive boulangerite, miargyrite and pyrite. It occurs in black ore (i) associated with galena, Pb-Sb sulfosalts (boulangerite, jamesonite) and Ag-Pb-Sb sulfosalts (andorite group minerals, freieslebenite and diaphorite) (Figure 5c,d). It is Minerals 2019, 9, 430 16 of 47 frequent in polished sections (160 point analyses). It was found as elongated lamellae up to 100 μm in length and 20 μm in width forming massive grains several hundred microns across. The chemical composition of owyheeiteratio ca. (Table 1:1 (Figure 7) is9 a); close a less to pronounced ideal formula positive Ag3Pb correlation10Sb11S28 was found between Ag and Sb with proposed by Moëlo et al. [44], with a slightratio ca.deficit 2:1 (Figureof Pb and9b). an Both excess correlations of Sb. Figure in principle 7 shows fit thethat line between zoubekite and boulangerite. contents of main elements Ag, Pb andThe Sb substitution do not correlate scheme significantly can be expressed and the as 2Pb Pb ↔AgAg + 0.5Sb.Sb The chemical composition of found substitution presented by Moëlo et al. [45Ag-poor] is not the Ag-Pb-Sb dominant sulfosalts factor in is closethe chemical to two mineral composition phases: of the recently described mineral tubulite owyheeite. The determined contents of seleniumAg2Pb22Sb in20 theS53 studied, which, mineral however, are di relativelyffers in its low very (0.12 unusual–1.17 and specific tube-like morphology [47]; apfu; 0.21–1.97 wt.%). Its average composition (113 analyses) is possible to express by empirical and an unnamed phase M3 with the ideal formula AgPb11Sb11S26 described by Megerskaja and formula (Ag2.96Cu0.03)Σ2.99(Pb9.63Fe0.02)Σ9.65(SbRyklMinerals11.18As [480.03 2019] from)Σ11.21(, 9, x PˇrS FOR27.73íbram,Se PEER0.36Cl CzechREVIEW0.04)Σ28.13 Republic. on the basis Other of unnamed52 apfu. phases in this system differ first of15 all of by 45 having higher Pb contents and lower Sb (Figure9a,b). The Se contents found in Ag-poor Ag-Pb-Sb sulfosalts are relatively low, within 0.22–1.54 at.% (0.18–1.35 wt.% Se). The chemical compositions and 11.8 corresponding10.2 formula coefficients calculated for 52 apfu (as in owyheeite) are given inGn Table8. (a) (b) 11.6 10.0 Aef

Table 8. EPMA data for Ag-poor Ag-Pb-Sb sulfosalts.Bou )

) 11.4

f f p

p 9.8 a

a Jms wt% apfu Σ52 Atoms

( (

Analyses s

11.2 e Aps

A F +

+ Ag Pb Fe Sb As Se S Total Ag Cu Pb Fe Sb As Se S b

b 9.6 P S 11.0 495 0.87 49.27 1.95 27.19 0.00 0.32 19.84Jms 99.43 0.37 0.01 10.93 1.60 10.27 0.02 0.19 28.44 1513 1.05 9.452.45 0.09 27.14 0.10 0.95 18.81 100.59 0.46 0.01 12.01 0.08 10.58 0.06 0.57 27.83 10.8 1325 1.17 52.47 0.46 26.70 0.00 0.55 18.94 100.29 0.52 0.02 12.06 0.39 10.45 0.02 0.33 28.14 904 1.18 51.61 0.00 28.04 Gn0.00 0.44 18.37 99.63 0.53 0.01 12.10 0.03 11.18 0.00 0.27 27.82 10.6 1559 2.02 9.251.78 0.00 27.01 0.09 0.37 18.33 99.60 0.91Bou 0.02 12.15 0.02 10.78 0.06 0.23 27.78 9.2 9.4 9.6 9.8 10.0 10.2 2.7 2.8 2.9 3.0 3.1 3.2 3.3 323 2.03 50.64 0.00 27.45 0.05 0.25 18.53 98.95 0.91 0.01 11.84 0.03 10.92 0.03 0.16 28.00 Pb+Fe (apfu) 991 2.21 50.36 0.00 27.19 0.00Ag+Cu 0.91 (apfu)18.82 99.49 0.98 0.00 11.62 0.02 10.68 0.03 0.55 28.07 490 2.36 47.86 0.94 28.64 0.05 0.36 19.53 99.73 1.01 0.01 10.69 0.78 10.89 0.03 0.21 28.19 321 2.26 48.55 0.07 27.80 0.10 0.18 18.68 97.64 1.01 0.00 11.36 0.06 11.07 0.06 0.11 28.24 Figure 7. Graph Ag + Cu vs Sb + As (apfu1502) (a) and2.48 Ag50.13 + Cu vs0.12 Pb +28.26 Fe (apfu0.10) (b) 1.35 for owyheeite18.87 101.30. 1.08 0.00 11.32 0.10 10.86 0.06 0.80 27.53 580 2.71 48.99 0.06 28.36 0.00 0.70 19.12 99.95 1.19 0.00 11.15 0.05 10.98 0.02 0.42 28.11 2227 2.69 50.88 0.06 26.61 0.00 0.20 18.81 99.25 1.20 0.02 11.81 0.05 10.51 0.00 0.12 28.22 891 2.87 47.51 0.12 29.17 0.00 0.48 19.37 99.52 1.25 0.01 10.75 0.10 11.23 0.00 0.29 28.32 2774 3.31 47.97 0.00 27.86 0.00 0.27 18.82 98.23 1.47 0.06 11.11 0.01 10.98 0.02 0.17 28.17 2775 3.53 47.84 0.00 28.02 0.07 0.29 18.66 98.41 1.57 0.08 11.09 300.00  m 11.05 0.05 0.18 27.95 578 3.92 46.80 0.00 29.39 0.05 0.42 18.77 99.34 1.72 0.01 10.71 0.04 11.44 0.03 0.25 27.75 895 4.29 45.97 0.00 28.46 0.00 0.51 18.90 98.12 1.89 0.02 10.55 0.02 11.12 0.01 0.31 28.04 1003 5.08 44.78 0.00 28.62 0.06 0.52 19.22 98.27 2.21 0.03 10.14 0.03 11.03 0.03 0.31 28.13 992Figure5.12 8. Grain43.91 of 0.06Ag-poor30.87 Ag-0.06Pb-Sb 0.89 sulfosalt19.28 (Ap 100.18s, 3.3 wt2.18.% Ag) 0.05 in boulangerite9.76 0.05 11.67 (Bou) in0.04 association 0.52 27.69 1389 5.16 43.81 0.09 30.32 0.00 0.39 20.05 99.82 2.18 0.00 9.63 0.07 11.34 0.02 0.22 28.47 with jamesonite (Jms), Ag-excess fizélyite (Aef) and galena (Gn). The succession runs as: galena – 909 5.20 44.51 0.00 28.46 0.00 0.55 18.90 97.62 2.29 0.01 10.20 0.01 11.09 0.02 0.33 27.98 boulangerite – jamesonite – Ag-poor Ag-Pb-Sb sulfosalt – Ag-excess fizélyite. Analyses are ordered according to increasing Ag content.

32 24 (a) Ag-poor Ag-Pb-Sb sulfosalts, this paper (b) 30 owyheeite, this paper 22 M3

28 Ag-poor Ag-Pb-Sb sulfosalts, published data ) ) boulangerite zoubekite

% 26 boulangerite

% T

20 .

UM1979-14 .

a (

( M2

24 s

e T F

UM1990-32 A

+ 18

22 M2 + b

b UM1979-14 UM1990-32 P M3 zoubekite S 20 16 Ag-poor Ag-Pb-Sb sulfosalts, this paper owyheeite, this paper 18 Ag-poor Ag-Pb-Sb sulfosalts, published data 16 14 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 Ag+Cu (at. %) Ag+Cu (at. %) FigureFigure 9. 9.(a) Graph Ag Ag ++ CuCu vs vs Pb Pb ++ FeFe (at.%) (at.%) for for Ag-poor Ag-poor Ag-Pb-Sb Ag-Pb-Sb sulfosalts sulfosalts and and owyheeite; owyheeite; boulangeriteboulangerite idealideal composition composition Pb Pb5Sb5Sb4S411S;11 T;-tubulite T-tubulite ideal ideal composition composition Ag2Pb Ag22Sb2Pb20S2253[4Sb720]; Sunnamed53 [47]; unnamedM3—Příbram M3—Pˇr [4íbram8]; unnamed [48]; unnamed M2— M2—PˇrPříbramíbram [48]; [48 UM1979]; UM1979-14—Primorye-14—Primorye [4 [499,50,50];]; UM1990-32; UM1990-32; zoubekitezoubekite ideal ideal composition composition AgPb44SSbb44SS1010 [46[46].(].(b)b )graph graph Ag Ag + Cu+ Cuvs. Sb vs. + As Sb (at.+ %As) for (at.%) Ag-poor for Ag-poorAg-Pb-Sb Ag-Pb-Sb sulfosalts sulfosalts and owyheeite; and owyheeite; boulangerite boulangerite ideal ideal composition composition Pb5Sb Pb4S511Sb; 4 TS-11tubulite; T-tubulite ideal

idealcomposition composition Ag2 AgPb222PbSb2022SSb53 20[47];S53 [47 unnamed]; unnamed M3 M3—Pˇr—Příbramíbram [48]; [48 ]; unnamed unnamed M2—PˇrM2—Příbramíbram [48 [48];]; UM1979-14—PrimoryeUM1979-14—Primorye [49 [49];]; UM1990-32 UM1990-32 [50 [50];]; zoubekite zoubekite ideal ideal composition composition AgPb AgPb4Sb4Sb4S4S1010 [[46].46].

Minerals 2019, 9, 430 17 of 47

4.3. Pb-Sb Sulfosalts

4.3.1. Boulangerite, Pb5Sb4S11 Boulangerite occurs as abundant lead grey felt-like aggregates and needle crystals in quartz cavities up to 1 cm or as massive grain needle-like aggregates several cm in size associated with galena and miargyrite in black ore type (i). In polished sections (170 point analyses), it occurs as needle-like and column-like crystals up to 80 µm in length and 10 µm in width associated with galena, freislebenite, jamesonite, andorite group minerals and pyrite (Figure2a,b, Figure5c, Figure8, Figure 10a,b) of black ore (i). Also occurs as lenses in white quartz of ore (iii) consisting of massive ﬁbrous and needle-like grains associated with jamesonite and galena. It belongs to the earliest minerals in the observed mineral associations, next to galena. Minerals 2019, 9, x FOR PEER REVIEW 17 of 45

(a) (b) Bou Bou Gn Bou Bou Aef

Frs Dia Aef Dia Bou Sms Bou Gn 20  m 50  m

Figure 10. (a) Ag-excess fizélyite (Aef) replaces boulangerite (Bou) of black ore (i). (b) earliest galena (Gn)Figure replaced 10. (a) Ag by- boulangeriteexcess fizélyite (Bou) (Aef) andreplaces semseyite boulangerite (Sms); (B semseyiteou) of black was ore subsequently (i). (b) earliest replaced galena by freieslebenite(Gn) replaced (Frs)by boulangerite and diaphorite (Bou (Dia).) and Bothsemseyite back-scattered (Sms); semseyite electron was (BSE) subsequently images. replaced by freieslebenite (Frs) and diaphorite (Dia). Both back-scattered electron (BSE) images. The chemical composition of boulangerite (Table9) is close to ideal stoichiometry; only traces of Fe, Mn and Ag were identified. In anion, contents of Se up to 0.63 apfu (2.69wt.%) (Figure 11) were observed, which is significantly more than in other Pb-Sb sulfosalts (jamesonite, semseyite). Its0.26 average composition (167 analyses) is possible to express by the empirical formula (Pb4.89Fe0.01Mn0.01)Σ4.92Sb4.03(S10.89Se0.12)Σ11.01 on the basis of 20 apfu. 0.24 Table 9. EPMA data for boulangerite. 0.22 wt.% apfu Σ20 Atoms Analyses Ag0.20 Pb Fe Mn Sb As Se S Total Ag Pb Fe Mn Sb As Se S 2468 0.00 55.00 0.16 0.15 25.47 0.00 0.00 18.50 99.28 0.00 5.02 0.05 0.05 3.96 0.00 0.00 10.91

Pb/total 2475 0.00 54.560.18 0.00 0.06 26.35 0.00 0.04 18.89 99.90 0.00 4.92 0.01 0.02 4.04 0.00 0.01 11.00 2226 0.25 54.29 0.11 0.06 26.35 0.00 0.09 18.71 99.86 0.04boulangerite 4.90 0.04 0.02 4.05 0.00 0.02 10.92 368 0.00 54.52 0.00 0.00 26.17 0.09 0.24 18.74 99.76 0.01semseyite 4.92 0.00 0.01 4.02 0.02 0.06 10.93 1644 0.12 55.080.16 0.00 0.00 25.10 0.10 0.31 18.54 99.24 0.02jamesonite 5.03 0.00 0.01 3.90 0.02 0.07 10.94 1855 0.00 54.74 0.00 0.00 26.35 0.08 0.59 18.64 100.39 0.00 4.93 0.00 0.00 4.04 0.02 0.14 10.85 1940 0.00 54.80 0.00 0.05 26.81 0.05 0.61 18.90 101.21 0.00 4.88 0.01 0.02 4.06 0.01 0.14 10.87 718 0.05 53.970.14 0.00 0.00 26.04 0.00 0.85 18.73 99.64 0.01 4.86 0.01 0.01 3.99 0.01 0.20 10.90 581 0.00 55.21 0.00 0.000.0026.12 0.000.02 1.07 18.590.04 101.000.06 0.00 4.950.08 0.00 0.01 0.103.99 0.01 0.25 10.78 757 0.00 54.13 0.17 0.00 25.62 0.00 1.93 18.25 100.09 0.00 4.89 0.06 0.01 3.93 0.00 0.46 10.64 Se/(Se+S) 1515 0.00 54.01 0.10 0.09 26.29 0.06 2.21 18.07 100.84 0.00 4.85 0.03 0.03 4.01 0.02 0.52 10.48 748 0.00 54.27 0.06 0.00 26.17 0.00 2.69 18.12 101.30 0.01 4.86 0.02 0.01 3.99 0.00 0.63 10.48 Figure 11. AnalysesGraph Se/(Se are ordered + S) (apfu according) vs Pb/total to increasing apfu for Se Pb content.-Sb sulfosalts.

Table 9. EPMA data for boulangerite.

wt.% apfu Ʃ20 Atoms Analyses Ag Pb Fe Mn Sb As Se S Total Ag Pb Fe Mn Sb As Se S 2468 0.00 55.00 0.16 0.15 25.47 0.00 0.00 18.50 99.28 0.00 5.02 0.05 0.05 3.96 0.00 0.00 10.91 2475 0.00 54.56 0.00 0.06 26.35 0.00 0.04 18.89 99.90 0.00 4.92 0.01 0.02 4.04 0.00 0.01 11.00 2226 0.25 54.29 0.11 0.06 26.35 0.00 0.09 18.71 99.86 0.04 4.90 0.04 0.02 4.05 0.00 0.02 10.92 368 0.00 54.52 0.00 0.00 26.17 0.09 0.24 18.74 99.76 0.01 4.92 0.00 0.01 4.02 0.02 0.06 10.93 1644 0.12 55.08 0.00 0.00 25.10 0.10 0.31 18.54 99.24 0.02 5.03 0.00 0.01 3.90 0.02 0.07 10.94 1855 0.00 54.74 0.00 0.00 26.35 0.08 0.59 18.64 100.39 0.00 4.93 0.00 0.00 4.04 0.02 0.14 10.85 1940 0.00 54.80 0.00 0.05 26.81 0.05 0.61 18.90 101.21 0.00 4.88 0.01 0.02 4.06 0.01 0.14 10.87 718 0.05 53.97 0.00 0.00 26.04 0.00 0.85 18.73 99.64 0.01 4.86 0.01 0.01 3.99 0.01 0.20 10.90 581 0.00 55.21 0.00 0.00 26.12 0.00 1.07 18.59 101.00 0.00 4.95 0.00 0.01 3.99 0.01 0.25 10.78 757 0.00 54.13 0.17 0.00 25.62 0.00 1.93 18.25 100.09 0.00 4.89 0.06 0.01 3.93 0.00 0.46 10.64 1515 0.00 54.01 0.10 0.09 26.29 0.06 2.21 18.07 100.84 0.00 4.85 0.03 0.03 4.01 0.02 0.52 10.48 748 0.00 54.27 0.06 0.00 26.17 0.00 2.69 18.12 101.30 0.01 4.86 0.02 0.01 3.99 0.00 0.63 10.48 Analyses are ordered according to increasing Se content.

Minerals 2019, 9, x FOR PEER REVIEW 17 of 45

(a) (b) Bou Bou Gn Bou Bou Aef

Frs Dia Aef Dia Bou Sms Bou Gn 20  m 50  m

Figure 10. (a) Ag-excess fizélyite (Aef) replaces boulangerite (Bou) of black ore (i). (b) earliest galena (Gn) replaced by boulangerite (Bou) and semseyite (Sms); semseyite was subsequently replaced by freieslebenite (Frs) and diaphorite (Dia). Both back-scattered electron (BSE) images. Minerals 2019, 9, 430 18 of 47

0.26

0.24

0.22

0.20

Pb/total 0.18 boulangerite semseyite 0.16 jamesonite

0.14 0.00 0.02 0.04 0.06 0.08 0.10 Se/(Se+S)

FigureFigure 11. 11.Graph Graph Se Se/(Se/(Se + S)+ S) (apfu (apfu) vs) vs Pb Pb/total/total apfu apfufor for Pb-Sb Pb-Sb sulfosalts. sulfosalts.

4.3.2. Semseyite, Pb9Sb8S21 Table 9. EPMA data for boulangerite.

Semseyite was found in awt.% similar association as boulangerite, but is muchapfu Ʃ20 rarer, Atoms it usually occurs Analyses as needle-likeAg or tabularPb Fe grain Mn up toSb 20 µAsm inSe length S andTotal 15 µmAg in widthPb Fe (Figure Mn 10Sbb). TheAs chemicalSe S composition2468 0.00 ofsemseyite 55.00 0.16 (Table 0.15 1025.47) corresponds 0.00 0.00 to ideal18.50 stoichiometry99.28 0.00 5.02 of this0.05 mineral 0.05 3.96 phase; 0.00 Ag 0.00 content 10.91 in one2475 point 0.00 analysis 54.56 (0.190.00 apfu0.06 ) can26.35 be 0.00 inﬂuenced 0.04 18.89 by the99.90 surrounding 0.00 4.92 phases.0.01 0.02 Unlike4.04 0.00 other 0.01 Pb-Sb 11.00 2226 0.25 54.29 0.11 0.06 26.35 0.00 0.09 18.71 99.86 0.04 4.90 0.04 0.02 4.05 0.00 0.02 10.92 sulfosalts,368 semseyite0.00 54.52 is0.00 virtually 0.00 26.17 Se-free 0.09 (Figure 0.24 1118.74). Its99.76 empirical 0.01 4.92 formula 0.00 (mean0.01 4.02 of 40.02 analyses) 0.06 10.93 is (Pb8.911644Ag 0.050.12)Σ8.96 55.08Sb7.95 0.00S21.08 0.00on the25.10 basis 0.10 of 380.31apfu 18.54. 99.24 0.02 5.03 0.00 0.01 3.90 0.02 0.07 10.94 1855 0.00 54.74 0.00 0.00 26.35 0.08 0.59 18.64 100.39 0.00 4.93 0.00 0.00 4.04 0.02 0.14 10.85 1940 0.00 54.80 0.00 0.05 26.81Table 0.05 10. EPMA0.61 data18.90 for101.21 semseyite. 0.00 4.88 0.01 0.02 4.06 0.01 0.14 10.87 718 0.05 53.97 0.00 0.00 26.04 0.00 0.85 18.73 99.64 0.01 4.86 0.01 0.01 3.99 0.01 0.20 10.90 581 0.00 55.21 0.00 0.00 26.12wt.% 0.00 1.07 18.59 101.00 apfu0.00 Σ4.9538 Atoms0.00 0.01 3.99 0.01 0.25 10.78 Analyses 757 0.00 54.13 0.17 0.00 25.62 0.00 1.93 18.25 100.09 0.00 4.89 0.06 0.01 3.93 0.00 0.46 10.64 Ag Pb Sb S Total Ag Pb Sb S 1515 0.00 54.01 0.10 0.09 26.29 0.06 2.21 18.07 100.84 0.00 4.85 0.03 0.03 4.01 0.02 0.52 10.48 748 0.00 54.272462 0.06 0.000.00 26.1752.82 0.00 27.46 2.69 19.53 18.12 99.92101.30 0.000.01 4.86 8.89 0.02 7.87 0.01 21.243.99 0.00 0.63 10.48 2482Analyses 0.57 50.70 are ordered 27.18 according 19.18 97.63 to increasing0.19 8.68Se content 7.92. 21.22 2483 0.00 52.41 27.04 18.81 98.42 0.00 9.05 7.95 21.00 2463 0.00 52.71 27.72 18.85 99.46 0.00 9.02 8.07 20.84

4.3.3. Jamesonite, Pb4FeSb6S14 Jamesonite occurs as needle crystals in quartz gangue or as massive grain needle-like aggregates up to 2 cm in black ore (i) and ore (iii). In the polished section, it was found as long needles up to 150 µm in length and 20 µm in width. It usually replaces galena and grows together with boulangerite, freibergite and pyrite (Figure2c, Figure8). It belongs to the earliest minerals in the association. The chemical composition of jamesonite (100 point analyses) is relatively uniform (Table 11) and close to ideal formula; only minor contents of Mn (up to 0.11 apfu) and Se (up to 0.27 apfu) were identiﬁed (Figure 11). The observed range of SeS 1 substitution is distinctly lower than in boulangerite − (Figure 11). The empirical formula for studied jamesonite on the basis of 25 apfu (mean of 84 analyses) can be expressed as Fe0.95Mn0.02)Σ0.97Pb3.94Sb6.05(S13.94Se0.07)Σ14.01. Minerals 2019, 9, 430 19 of 47

Table 11. EPMA data for jamesonite.

wt.% apfu Σ20 Atoms Analyses Pb Fe Mn Sb Se S Total Pb Fe Mn Sb Se S 2450 39.14 2.55 0.09 34.95 0.00 21.77 98.50 3.92 0.95 0.03 5.96 0.00 14.10 379 40.51 2.56 0.00 35.12 0.09 21.90 100.17 4.02 0.94 0.02 5.93 0.02 14.03 213 39.67 2.61 0.00 35.80 0.30 21.22 99.60 3.99 0.98 0.01 6.13 0.08 13.80 864 39.45 2.47 0.06 35.44 0.41 21.70 99.53 3.93 0.91 0.02 6.01 0.11 13.98 1304 39.29 2.62 0.10 35.76 0.43 21.91 100.09 3.88 0.96 0.04 6.01 0.11 13.99 863 39.69 2.41 0.10 36.12 0.44 21.74 100.49 3.93 0.89 0.04 6.08 0.11 13.90 1906 39.24 2.51 0.05 36.05 0.61 21.88 100.34 3.87 0.92 0.02 6.06 0.16 13.96 2069 38.48 2.45 0.14 35.56 0.83 20.81 98.27 3.92 0.93 0.05 6.16 0.22 13.70 Analyses are ordered according to increasing Se content.

4.4. Ag-Sb Sulfosalts

4.4.1. Miargyrite, AgSbS2 Miargyrite is by far the most abundant silver mineral in the Kutná Hora ore district, together with freibergite. Short column-like grey-black crystals of miargyrite up to 10 mm in size in cavities of milky quartz gangue (ore (iii)), or quartz–kutnohorite gangue (ore (ii)) are famous from this locality [36]. Frequently, miargyrite forms massive grain aggregates and lenses in all three types of oreMinerals of several 2019, 9, x centimetresFOR PEER REVIEW in size, often intergrowing with other Ag minerals such as pyrargyrite,19 of 45 diaphorite, freibergite and freieslebenite. In polished sections, it was found as groups of anhedral grains several hundred μm in size and occasional euhedral crystals into cavities. It appears in two grains several hundred µm in size and occasional euhedral crystals into cavities. It appears in two generations at least, the latter being characteristic of a considerably smaller size of grains (up to 20 generations at least, the latter being characteristic of a considerably smaller size of grains (up to 20 µm), μm), higher selenium content (Figure 12a) and the association of members of galena – clausthalite highersolid solution. selenium The content two generatio (Figure ns12 a)appear and thein all association three of the of membersabove-mentioned of galena ores – clausthalite (i, ii and iii), solid solution.examples The of miargyrite two generations in black appear ore (i)in are all in three Figure ofs the 2c– above-mentionede and 12a; red ore ores(ii) in (i, Figure ii ands iii), 12b examples and ore of miargyrite(iii) in Figure in black2f. ore (i) are in Figures2c–e and 12a; red ore (ii) in Figure 12b and ore (iii) in Figure2f.

(a) (b) Sp Mia Aef Mia Dia Gn Dia

Gn Sp Aef Agd Py

Py 200  m 40 m

Figure 12. (a) Galena (Gn)—the earliest mineral in the association—is replaced by diaphorite (Dia), whichFigure is 12. subsequently (a) Galena (G replacedn)—the byearliest Ag-excess mineral ﬁz éinlyite the (Aef).association Both— mineralsis replaced are by replaced diaphorite by miargyrite (Dia), (Mia),which whereas is subsequently miargyrite replaced with1 wt.% by Ag Se-excess (darker) fiz isélyite replaced (Aef). by Both the the minerals second-generation are replaced Se-rich by miargyritemiargyrite (lighter,(Mia), 5%whereas Se). (b) mi miargyriteargyrite with1 (Mia) embeddedwt.% Se in(darker) sphalerite is (Sp). replaced An argyrodite by the the (Agd) inclusionsecond-gener is onation the Se boundary-rich miargyrite between (lighter, sphalerite 5% Se). and (b) pyritemiargyrite (Py), (Mia) both embedded minerals (miargyritein sphalerite and argyrodite)(Sp). An argyrodite replace sphalerite. (Agd) inclusion Both back-scattered is on the boundary electron between (BSE) images. sphalerite and pyrite (Py), both minerals (miargyrite and argyrodite) replace sphalerite. Both back-scattered electron (BSE) images. Chemical analyses of miargyrite (175 points) revealed interesting Se contents (Figure 13a,b), otherwiseChemical it is closeanalyses to theof miargyrite ideal formula. (175 points) Determined revealed traces interesting of Pb, Cu Se andcontents Fe in (Figure someof 13 analyses a,b), otherwise it is close to the ideal formula. Determined traces of Pb, Cu and Fe in some of analyses are probably caused by microscopic intergrowths with other phases; irregular contents of As do not exceed 0.01 apfu (0.19 wt.%). The prevailing earlier generation of miargyrite contains up to 0.08 apfu (2.29 wt.%) of Se; the later generation of miargyrite shows a considerably larger extent of the SeS-1 substitution, usually between 0.11 and 0.35 apfu, corresponding to the maximum Se content of 8.79 wt.%. Two exceptionally high Se contents were measured in small anhedral grains of miargyrite in sphalerite of red ore (ii), belonging to the later generation. These show 0.57 and 0.62 apfu Se (14.54– 15.34 wt.% of Se)—not included in Table 12 due to increased Zn content from neighbouring sphalerite. The more significant contents of Se in miargyrite were so far described only by Nekrasov, Lunin [51] and Yunfen et al. [52]. The representative chemical analyses of both miargyrite generation and corresponding empirical formulae are given in Table 12.

0.5 60

(a) 55 (b) 0.4 miargyrite I miargyrite II 50

0.3 )

) 45

. miargyrite t a 40

0.2 a

( (

pyrargyrite

g stephanite S A 35 0.1 polybasite 30

0.0 25

20 1.5 1.6 1.7 1.8 1.9 2.0 2.1 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 S ( apfu) Se/(S+Se)

Minerals 2019, 9, x FOR PEER REVIEW 19 of 45

grains several hundred μm in size and occasional euhedral crystals into cavities. It appears in two generations at least, the latter being characteristic of a considerably smaller size of grains (up to 20 μm), higher selenium content (Figure 12a) and the association of members of galena – clausthalite solid solution. The two generations appear in all three of the above-mentioned ores (i, ii and iii), examples of miargyrite in black ore (i) are in Figures 2c–e and 12a; red ore (ii) in Figures 12b and ore (iii) in Figure 2f.

(a) (b) Sp Mia Aef Mia Dia Gn Dia

Gn Sp Aef Agd Py

Py 200  m 40 m

Figure 12. (a) Galena (Gn)—the earliest mineral in the association—is replaced by diaphorite (Dia), which is subsequently replaced by Ag-excess fizélyite (Aef). Both minerals are replaced by miargyrite (Mia), whereas miargyrite with1 wt.% Se (darker) is replaced by the the second-generation Se-rich miargyrite (lighter, 5% Se). (b) miargyrite (Mia) embedded in sphalerite (Sp). An argyrodite (Agd) inclusion is on the boundary between sphalerite and pyrite (Py), both minerals (miargyrite and argyrodite) replace sphalerite. Both back-scattered electron (BSE) images.

Chemical analyses of miargyrite (175 points) revealed interesting Se contents (Figure 13 a,b), Mineralsotherwise2019 ,it9 ,is 430 close to the ideal formula. Determined traces of Pb, Cu and Fe in some of analyses20 of are 47 probably caused by microscopic intergrowths with other phases; irregular contents of As do not areexceed probably 0.01 apfu caused (0.19 by wt. microscopic%). The prevailing intergrowths earlier with generation other phases; of miargyrite irregular contains contents up of to As 0.08 do apfu not exceed(2.29 wt. 0.01%) apfuof Se(0.19; the wt.%).later generation The prevailing of miargyrite earlier generation shows a considerably of miargyrite larger contains extent up toof 0.08the apfuSeS-1 substitution, usually between 0.11 and 0.35 apfu, corresponding to the maximum Se content of 8.79 (2.29 wt.%) of Se; the later generation of miargyrite shows a considerably larger extent of the SeS 1 − substitution,wt.%. Two exceptionally usually between high 0.11 Seand contents 0.35 apfu were, corresponding measured in tosmall the maximum anhedral grains Se content of miargyrite of 8.79 wt.%. in Twosphalerite exceptionally of red ore high (ii), Se belonging contents were to the measured later generation. in small anhedral These show grains 0.57 of and miargyrite 0.62 apfu in sphaleriteSe (14.54– of15.34 red ore wt. (ii),% of belonging Se)—not to included the later generation. in Table 12 These due show to increased 0.57 and Zn0.62 contentapfu Se (14.54–15.34 from neighbouring wt.% of Se)—notsphalerite. included The more in Tablesignificant 12 due contents to increased of Se in Zn miargyrite content from were neighbouring so far described sphalerite. only by Nekrasov, The more signiﬁcantLunin [51]contents and Yunfen of Se et in al. miargyrite [52]. The representative were so far described chemical only analyses by Nekrasov, of both Lunin miargyrite [51] and generation Yunfen etand al. corresponding [52]. The representative empirical formulae chemical are analyses given in of Table both miargyrite12. generation and corresponding empirical formulae are given in Table 12.

0.5 60

(a) 55 (b) 0.4 miargyrite I miargyrite II 50

0.3 )

) 45

. miargyrite t a 40

0.2 a

( (

pyrargyrite

g stephanite S A 35 0.1 polybasite 30

0.0 25

20 1.5 1.6 1.7 1.8 1.9 2.0 2.1 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 S ( apfu) Se/(S+Se)

Figure 13. (a) Graph S vs Se (apfu) for two types of miargyrite. (b) graph Se/(S + Se) vs Ag (at.%) for Ag-Sb-S mineral phases.

Table 12. EPMA data for miargyrite.

wt.% apfu Σ4 Atoms Analyses Ag Pb Fe Sb As Se S Total Ag Cu Pb Fe Cd Sb As Se S 514 37.18 0.00 0.00 41.06 0.17 0.00 21.83 100.23 1.01 0.00 0.00 0.00 0.00 0.99 0.01 0.00 1.99 52 36.32 0.10 0.06 41.47 0.08 0.33 21.47 99.83 0.99 0.00 0.00 0.00 0.00 1.01 0.00 0.01 1.98 57 35.95 0.23 0.07 40.80 0.13 0.51 21.65 99.34 0.98 0.00 0.00 0.00 0.00 0.99 0.01 0.02 1.99 58 35.99 0.34 0.08 41.10 0.10 0.69 21.32 99.62 0.99 0.00 0.00 0.00 0.00 1.00 0.00 0.03 1.97 8 36.35 0.10 0.00 41.74 0.08 0.88 21.36 100.51 0.99 0.00 0.00 0.00 0.00 1.01 0.00 0.03 1.96 1963 36.13 0.06 0.00 41.81 0.07 1.08 21.05 100.18 0.99 0.00 0.00 0.00 0.00 1.02 0.00 0.04 1.94 791 35.67 0.20 0.06 40.68 0.10 1.76 20.70 99.16 0.99 0.00 0.00 0.00 0.00 1.00 0.00 0.07 1.93 539 36.42 0.08 0.00 41.05 0.07 3.46 20.09 101.18 1.00 0.00 0.00 0.00 0.00 1.00 0.00 0.13 1.86 1137 35.57 0.09 0.00 40.44 0.00 4.26 19.13 99.50 1.00 0.00 0.00 0.00 0.00 1.01 0.00 0.16 1.82 1362 35.16 0.06 0.16 40.10 0.05 4.92 19.53 99.99 0.98 0.00 0.00 0.01 0.00 0.99 0.00 0.19 1.83 1138 34.97 0.40 0.00 40.01 0.00 5.63 18.40 99.40 1.00 0.00 0.01 0.00 0.00 1.01 0.00 0.22 1.76 1265 35.18 0.21 0.08 40.05 0.06 6.35 18.19 100.12 1.00 0.00 0.00 0.00 0.00 1.01 0.00 0.25 1.74 2699 35.18 0.08 0.46 39.06 0.00 8.65 16.85 100.27 1.01 0.00 0.00 0.03 0.00 0.99 0.00 0.34 1.63 2700 34.83 0.06 0.40 38.93 0.00 8.79 16.34 99.34 1.01 0.00 0.00 0.02 0.00 1.00 0.00 0.35 1.60 Analyses are ordered according to increasing Se content.

Figure 13. (a) Graph S vs Se (apfu) for two types of miargyrite. (b) graph Se/(S + Se) vs Ag (at.%) for Ag-Sb-S mineral phases.

Table 12. EPMA data for miargyrite.

wt.% apfu Ʃ4 Atoms Analyses Ag Pb Fe Sb As Se S Total Ag Cu Pb Fe Cd Sb As Se S 514 37.18 0.00 0.00 41.06 0.17 0.00 21.83 100.23 1.01 0.00 0.00 0.00 0.00 0.99 0.01 0.00 1.99 52 36.32 0.10 0.06 41.47 0.08 0.33 21.47 99.83 0.99 0.00 0.00 0.00 0.00 1.01 0.00 0.01 1.98 57 35.95 0.23 0.07 40.80 0.13 0.51 21.65 99.34 0.98 0.00 0.00 0.00 0.00 0.99 0.01 0.02 1.99 58 35.99 0.34 0.08 41.10 0.10 0.69 21.32 99.62 0.99 0.00 0.00 0.00 0.00 1.00 0.00 0.03 1.97 8 36.35 0.10 0.00 41.74 0.08 0.88 21.36 100.51 0.99 0.00 0.00 0.00 0.00 1.01 0.00 0.03 1.96 1963 36.13 0.06 0.00 41.81 0.07 1.08 21.05 100.18 0.99 0.00 0.00 0.00 0.00 1.02 0.00 0.04 1.94 791 35.67 0.20 0.06 40.68 0.10 1.76 20.70 99.16 0.99 0.00 0.00 0.00 0.00 1.00 0.00 0.07 1.93 539 36.42 0.08 0.00 41.05 0.07 3.46 20.09 101.18 1.00 0.00 0.00 0.00 0.00 1.00 0.00 0.13 1.86 1137 35.57 0.09 0.00 40.44 0.00 4.26 19.13 99.50 1.00 0.00 0.00 0.00 0.00 1.01 0.00 0.16 1.82 1362 35.16 0.06 0.16 40.10 0.05 4.92 19.53 99.99 0.98 0.00 0.00 0.01 0.00 0.99 0.00 0.19 1.83 1138 34.97 0.40 0.00 40.01 0.00 5.63 18.40 99.40 1.00 0.00 0.01 0.00 0.00 1.01 0.00 0.22 1.76 1265 35.18 0.21 0.08 40.05 0.06 6.35 18.19 100.12 1.00 0.00 0.00 0.00 0.00 1.01 0.00 0.25 1.74 2699 35.18 0.08 0.46 39.06 0.00 8.65 16.85 100.27 1.01 0.00 0.00 0.03 0.00 0.99 0.00 0.34 1.63 2700 34.83 0.06 0.40 38.93 0.00 8.79 16.34 99.34 1.01 0.00 0.00 0.02 0.00 1.00 0.00 0.35 1.60 Analyses are ordered according to increasing Se content.

4.4.2. Pyrargyrite, Ag3SbS3 Pyrargyrite crystals up to 5 mm in size and massive grain aggregates several cm in size, occurring (less abundantly than miargyrite) in milky quartz gangue associated with miargyrite and freibergite of ore (iii) or in cavities of the kutnohorite–quartz gangue of red ore (ii), associated with other Ag-Sb sulfides and pyrite. Only three samples of pyrargyrite were found in black ore (i) (Figure 2a). In polished sections pyrargyrite was found in nine samples (40 point analyses) as Mineralsanhedral2019 grains, 9, 430 up to 30 μm. It often forms thin veinlets as much as 200 μm in length and 20 μm21 in of 47 width. It occurs as a filling of thin fissures in miargyrite in a close vicinity of Au-rich silver. It also occurs in drop-shaped inclusions of galena in pyrite of red ore (ii) where it replaces galena (Figure of14a). pyrargyrite The chemical and composition the corresponding of pyrargyrite chemical and formulaethe corresponding are given chemical in Table formulae 13. In comparison are given in to miargyriteTable 13. In and comparison stephanite to (Figure miargyrite 13b), and the stephanitedetermined (Figure range of13b SeS), the1 substitution determined in range pyrargyrite of SeS-1 is − limited,substitution maximum in pyrargyrit is 0.13 apfue is limited,(1.82 wt.%) maximum in one analysis,is 0.13 apfu but (1.82 in all wt. others%) in does one notanalysis, exceed but 0.70 in wt.%). all Theothers found does As not contents exceed in 0.70 pyrargyrite wt.%). The (solid found solution As contents with proustite) in pyrargyrite are very (solid low (upsolution to 0.02 withapfu , i.e.,proustite) 0.21 wt.%), are very similar low to (up As to contents 0.02 apfu in, alli.e., primary 0.21 wt. sulfosalts%), similar of to the As hypogene contents mineralization in all primary in Kutnsulfosaltsá Hora. of the hypogene mineralization in Kutná Hora.

(a) (b)

Prg Py Nau

Ste Py Ste Py

20  m 10  m

Figure 14. (a) An inclusion in pyrite (Py) of red ore (ii): stephanite (Ste), which is a prevailing mineral inFigure the inclusion 14. (a) An replaces inclusion pyrargyrite in pyrite (Py) (Prg). of red Remnants ore (ii): ofstephanite original galena(Ste), which (white is spots)a prevailing which mineral was later replacedin the inclusion by pyrargyrite replaces arepyrargyrite visible at (Prg) the bottom. Remnants part of of original the grain. galena (b) euhedral (white spots) crystal which in pyrite was later (Py) of redreplaced ore (ii) by formed pyrargyrite by two are Ag-rich visible at mineral the bottom phases: part naumannite of the grain. (Nau) (b) euhedral is replaced crystal by stephanitein pyrite (Py) (Ste). Both back-scattered electron (BSE) images.

Table 13. EPMA data for pyrargyrite.

wt.% apfu Σ7 Atoms Analyses Ag Pb Cd Sb As Se S Total Ag Pb Cd Sb As Se S 2329 59.10 0.00 0.00 22.77 0.00 0.00 17.51 99.38 2.99 0.00 0.00 1.02 0.00 0.00 2.98 2471 59.38 0.07 0.08 22.95 0.00 0.00 18.13 100.60 2.95 0.00 0.00 1.01 0.00 0.00 3.03 2522 60.14 0.16 0.12 22.23 0.00 0.11 17.90 100.66 3.00 0.00 0.01 0.98 0.00 0.01 3.00 2528 61.11 0.00 0.00 21.94 0.00 0.15 17.63 100.83 3.02 0.00 0.00 0.96 0.00 0.01 2.93 2622 59.22 0.06 0.10 22.67 0.21 0.64 16.70 99.60 3.02 0.00 0.00 1.03 0.02 0.04 2.87 2729 61.69 0.00 0.00 21.74 0.00 0.69 17.53 101.65 3.06 0.00 0.00 0.96 0.00 0.05 2.93 Analyses are ordered according to increasing Se content.

4.4.3. Pyrostilpnite, Ag3SbS3 Orange to bright red leaﬂets and coatings of pyrostilpnite on fractures of quartz gangue were described by Vepˇrek[53]. Later, Mrázek and Zeman [17] found orange-red elongated transparent crystalas up to 4 mm in length with intensive lustre in cavities of quartz gangue from the Vein I and Vein A (ore (iii)), determined by X-ray diﬀraction. In backscatter electron images, pyrostilpnite was not distinguished from its isochemical dimorph, pyrargyrite. However, orange crystals of pyrostilpnite under veinlets of pyragyrite were observed in optical microscope.

4.4.4. Stephanite, Ag5SbS4 Stephanite occurs in red ore (ii) from the Vein B as rare anhedral grains up to 20 µm in size in fractures of miargyrite or as inclusions in miargyrite (Figure2e), accompanied by exsolutions of pyrargyrite, itself being replaced by acanthite. It belongs to later minerals in the studied association. Minerals 2019, 9, 430 22 of 47

It also occurs among drop-shaped inclusions in pyrite of red ore (ii), often rich in selenium (as much as 9.8 wt.% of Se) (Figure 14a,b and Figure 20b) or veinlets in miargyrite of red ore (ii) (Figure 24a). The chemical composition of stephanite and the corresponding chemical formulae are given in Table 14. One grain of stephanite is characteristic of a very high Se content of as much as 1.11 apfu (9.84 wt.%, not included in Table 14 due to a lower total). Thus, stephanite—together with miargyrite—is the mineral with the highest determined range of the SeS 1 substitution among Ag-Sb-S mineral phases − (Figure 13b). The selenium analogue of stephanite—the mineral selenostephanite—was described from two Russian deposits—Rudnaya Sopka, Chukotka [54] and Julietta, Magadan region [55]—and requires 17.3 or more wt.% of Se.

Table 14. EPMA data for stephanite.

wt.% apfu Σ10 Atoms Analyses Ag Cd Sb As Se S Total Ag Cd Sb As Se S 2343 68.62 0.15 16.64 0.13 0.00 16.03 101.57 4.98 0.01 1.07 0.01 0.00 3.91 2524 67.43 0.22 14.31 0.00 0.00 15.66 97.63 5.06 0.02 0.95 0.00 0.00 3.95 2525 67.76 0.13 15.00 0.02 0.00 16.18 99.10 4.99 0.01 0.98 0.00 0.00 4.01 Minerals 20192755, 9, x FOR68.74 PEER REVIEW 0.00 14.07 0.00 0.00 15.64 98.45 5.13 0.00 0.93 0.00 0.0022 3.92 of 45 2732 69.39 0.00 13.88 0.00 1.18 15.37 99.81 5.13 0.00 0.91 0.00 0.12 3.82 red ore 2747(ii) (Figure66.97 15a,b). 0.00 Polybasite 14.43 0.03is in a 1.70 close 14.31 contact97.44 with Se5.14-rich acanthite 0.00 0.98 and 0.00 both 0.18 minerals 3.69 replace galena. Associated Analyses minerals are form ordereding accordinginclusions to increasing in pyrite Se but content. not in a direct contact with polybasite include argyrodite, pyrargyrite, aguilarite, clausthalite and naumannite. Polybasite differs in minor but essential Cu content from chemically similar stephanite and also 4.4.5.by a different Polybasite, (Ag [Ag + Cu)/(Sb9CuS4] [(Ag,Cu)+ As) ratio.6(Sb,As) Copper2S7 ]contents of only 0.22–0.44 apfu are lower than for minerals of polybasite group in the literature [56]; low contents of copper are characteristic Polybasite was found in four grains of two samples (8 point analyses) as very rare euhedral especially of selenium-containing members of this group [57]. Determined contents of Se in the table-like crystals 40 µm in length and 10 µm in width, cutting across galena inclusions in pyrite of red range 0.07–0.76 apfu (Figure 13b) in samples from Padua mine are lower than the minimal limit (>1 ore (ii) (Figure 15a,b). Polybasite is in a close contact with Se-rich acanthite and both minerals replace Se apfu) for selenopolybasite [57]. The content of the pearceite component in studied sample is low galena.and does Associated not exceed minerals 0.17 apfu formingAs (0.55 wt. inclusions%). The chemical in pyrite analyses but not of in pol a directybasite contact and corresponding with polybasite includeempirical argyrodite, formulae pyrargyrite,are given in Table aguilarite, 15. clausthalite and naumannite.

(a) (b)

Py Aca Gn

Py Gn Gn Plb

Gn Py Plb Aca

30  m 20  m

Figure 15. (a) Euhedral tabular crystal of polybasite (Plb) associated with Se-rich acanthite (Aca). BothFigure minerals 15. (a) E replaceuhedral galena tabular (Gn). crystal (b ) of euhedral polybasite tabular (Plb) crystal associated of polybasite with Se-rich (Plb) acanthite growing (Ac acrossa). galena,Both minerals which occursreplace asgalena anhedral (Gn). inclusions(b) euhedral up tabula to severalr crystal tens of ofpolybasiteµm in pyrite (Plb) (Py)growing of red across ore (ii). Bothgalena back-scattered, which occurs electron as anhedral (BSE) inclusions images. up to several tens of μm in pyrite (Py) of red ore (ii). Both back-scattered electron (BSE) images. Polybasite diﬀers in minor but essential Cu content from chemically similar stephanite and also by a diﬀerent (Ag + Cu)/(SbTable+ As) 15. EPMA ratio. data Copper for polybasite contents. of only 0.22–0.44 apfu are lower than for minerals of polybasitewt.% group in the literature [56]; low contentsapfu Ʃ of29 Atoms copper are characteristic Analyses especiallyAg of selenium-containingCu Pb Fe Cd Sb members As Se of thisS groupTotal [57Ag]. DeterminedCu Pb Fe contentsCd Sb ofAs Se inSe the rangeS 2589 71.20 0.61 0.51 0.30 0.13 10.72 0.04 0.95 14.97 99.43 15.36 0.22 0.06 0.13 0.03 2.05 0.01 0.28 10.87 2587 71.45 0.69 0.74 0.54 0.17 11.85 0.03 1.01 15.96 102.43 14.82 0.24 0.08 0.22 0.03 2.18 0.01 0.29 11.14 2595 70.62 1.11 0.08 0.72 0.14 9.67 0.55 2.61 14.81 100.31 14.97 0.40 0.01 0.30 0.03 1.82 0.17 0.76 10.56 Analyses are ordered according to increasing Se content.

4.5. Minerals of the Tetrahedrite Series

4.5.1. Freibergite, Ag6[Cu4Fe2]Sb4S13−x Freibergite, together with miargyrite, is the most abundant silver mineral observed in the studied material (193 analyses). Freibergite occurs as crystals several mm in size in cavities of quartz–kutnohorite gangue (red ore (ii)) or in cavities of milky white quartz (ore (iii)) or grain aggregates several cm in size associated with miargyrite and pyrargyrite (ores (ii) and (iii)). In polished sections, it was frequently found also in black ore (i), and it forms anhedral grains up to 300 μm in size. The grains are often zonal, growth zones differ by silver content, negatively correlated with the copper content. Freibergite grows together intimately with diaphorite and freieslebenite, usually being replaced by miargyrite. An example of freibergite in black ore (i) is shown in Figure 2c; freibergite in red ore (ii) is shown in Figures 16a,b; and ore (iii) is shown in Figure 2f. The status of Ag-rich members of tetrahedrite group (freibergite, argentotennantite) and especially their boundaries with tetrahedrite and tennantite, is still being investigated [44]. Some

Minerals 2019, 9, 430 23 of 47

0.07–0.76 apfu (Figure 13b) in samples from Padua mine are lower than the minimal limit (>1 Se apfu) for selenopolybasite [57]. The content of the pearceite component in studied sample is low and does not exceed 0.17 apfu As (0.55 wt.%). The chemical analyses of polybasite and corresponding empirical formulae are given in Table 15.

4.5. Minerals of the Tetrahedrite Series

Freibergite, Ag6[Cu4Fe2]Sb4S13 x − Freibergite, together with miargyrite, is the most abundant silver mineral observed in the studied material (193 analyses). Freibergite occurs as crystals several mm in size in cavities of quartz–kutnohorite gangue (red ore (ii)) or in cavities of milky white quartz (ore (iii)) or grain aggregates several cm in size associated with miargyrite and pyrargyrite (ores (ii) and (iii)). In polished sections, it was frequently found also in black ore (i), and it forms anhedral grains up to 300 µm in size. The grains are often zonal, growth zones differ by silver content, negatively correlated with the copper content. Freibergite grows together intimately with diaphorite and freieslebenite, usually being replaced by miargyrite. An example of freibergite in black ore (i) is shown in Figure2c; freibergite in red ore (ii) is shown in Figure 16a,b; and ore (iii) is shown in Figure2f. The status of Ag-rich members of tetrahedrite group (freibergite, argentotennantite) and especially their boundaries with tetrahedrite and tennantite, is still being investigated [44]. Some authors have proposed a minimum content for freibergite of 4 apfu Ag [44,58], and a condition of Ag > Cu for argentotennantite (about 5 apfu Ag) [59]. On the basis of the results of crystal structure studies [58,60] and analyses of natural samples [61,62], Ag preferentially occupies the triangular A position with total content 6 apfu, and according to the present rules of mineralogical nomenclature [31], the boundary would be 3 apfu Ag [62]. Two groups of compositions were identified. The majority of analyses (Table 16) represent typical freibergite with more than 4 apfu of Ag. Its chemical composition is fairly monotonous with regard to Fe/Zn and Sb/As ratios. Iron is always dominant, and As is not present, as is the case with all sulfosalts in hypogene mineralization in Kutná Hora. Zonality phenomena are visible in some grains quite profoundly, however, differing only moderately in terms of Ag/Cu ratio. Ag contents were determined from 3.99 apfu (23.33 wt.%) to 7.25 apfu (38.61 wt.%) in freibergite, indicating that the placement of Ag not only in the A position (up to 6 apfu), but also to a limited degree in the B position (up to 1.25 apfu) takes place. Freibergite with as much as 46.4 wt.% of Ag (8.93 apfu) was described from the Rejzské pásmo Lode in the Kutná Hora ore district [18]. This phase corresponds to the newly approved mineral rozhdestvenskayaite [63]. Ag and Cu contents show an excellent negative correlation (Figure 17a), which is in agreement with published results (e.g., [35,64,65]). In the case of freibergite below 6 apfu Ag, the rest of the A position is filled with copper. The B position, in addition to Ag contents (up to 0.40 apfu), is occupied by dominant Cu. In the C position, Fe (1.09–2.02 apfu) prevails over Zn (0.03–0.98 apfu), which is typical of freibergite (Figure 17b). Determined Ag/Cu ratios show no apparent correlation with Fe/Zn ratios. In the X position, the dominant Sb is in a part of analyses accompanied by negligible As, not exceeding 0.09 apfu (0.36 wt.%). The second group of analyses corresponds to members at the boundary between freibergite and Ag-rich tetrahedrite. This member is very rare and was found only in one sample of black ore (i) as anhedral grains associated with galena, freieslebenite, diaphorite, owyheeite and Ag-excess fizélyite. Ag content varies from 17.41 to 18.48 wt.%, corresponding to 2.93 to 3.15 apfu Ag, which is appreciably less than a typical common member of the tetrahedrite series, which is freibergite on all lodes of the Kutná Hore ore district. The chemistry is similar to freibergite in the respect that iron prevails over zinc, no arsenic substitutes for antimony (Table 17), and the substitution of Se for S is non-existent, although surrounding minerals contain as much as 1.1 wt.% of Se Minerals 2019, 9, 430 24 of 47

Table 15. EPMA data for polybasite.

wt.% apfu Σ29 Atoms Analyses Ag Cu Pb Fe Cd Sb As Se S Total Ag Cu Pb Fe Cd Sb As Se S 2589 71.20 0.61 0.51 0.30 0.13 10.72 0.04 0.95 14.97 99.43 15.36 0.22 0.06 0.13 0.03 2.05 0.01 0.28 10.87 2587 71.45 0.69 0.74 0.54 0.17 11.85 0.03 1.01 15.96 102.43 14.82 0.24 0.08 0.22 0.03 2.18 0.01 0.29 11.14 2595 70.62 1.11 0.08 0.72 0.14 9.67 0.55 2.61 14.81 100.31 14.97 0.40 0.01 0.30 0.03 1.82 0.17 0.76 10.56 Analyses are ordered according to increasing Se content.

Table 16. EPMA data for freibergite.

wt.% apfu Σ29 atoms Analyses Ag Cu Fe Zn Sb As Se S Total Ag Cu Fe Zn Sb As Se S Ag/A Cu/B 2419 23.33 20.84 4.72 1.64 26.83 0.01 0.00 22.34 99.71 3.99 6.05 1.56 0.46 4.07 0.00 0.00 12.85 3.99 4.04 2547 26.62 18.16 5.07 1.64 26.72 0.03 0.13 22.68 101.04 4.54 5.25 1.67 0.46 4.03 0.01 0.03 13.00 4.54 3.79 2548 27.49 17.76 5.15 1.90 26.65 0.08 0.12 22.50 101.66 4.68 5.13 1.69 0.53 4.02 0.02 0.03 12.88 4.68 3.81 2549 27.83 17.54 4.95 1.72 26.74 0.00 0.13 22.42 101.32 4.76 5.10 1.64 0.49 4.06 0.01 0.03 12.91 4.76 3.86 2246 28.78 16.57 5.30 0.97 26.48 0.00 0.00 21.46 99.56 5.07 4.96 1.80 0.28 4.14 0.00 0.00 12.73 5.07 4.03 812 29.59 14.64 5.27 1.00 26.38 0.15 0.00 21.58 98.61 5.27 4.43 1.81 0.29 4.16 0.04 0.00 12.93 5.27 3.70 63 31.22 15.18 3.41 3.16 25.69 0.19 0.00 21.09 99.94 5.56 4.59 1.17 0.93 4.05 0.05 0.00 12.63 5.56 4.15 811 32.11 13.60 4.97 1.12 26.29 0.11 0.00 21.45 99.66 5.73 4.12 1.72 0.33 4.16 0.03 0.00 12.88 5.73 3.86 67 33.24 14.09 3.48 2.95 25.61 0.22 0.00 21.06 100.65 5.92 4.26 1.20 0.87 4.04 0.06 0.00 12.62 5.92 4.18 1461 33.55 13.78 5.01 1.07 25.59 0.11 0.00 20.91 100.01 6.02 4.19 1.74 0.32 4.07 0.03 0.00 12.62 6.00 4.19 42 33.87 13.64 3.56 2.63 25.63 0.21 0.00 20.52 100.06 6.12 4.19 1.24 0.78 4.11 0.05 0.00 12.48 6.00 4.19 36 34.60 13.45 3.75 2.30 25.69 0.23 0.00 20.65 100.67 6.22 4.11 1.30 0.68 4.09 0.06 0.00 12.50 6.00 4.11 2142 34.80 13.03 5.58 0.11 26.15 0.00 0.00 20.44 100.11 6.31 4.01 1.95 0.03 4.20 0.00 0.00 12.47 6.00 4.01 2140 36.99 12.32 5.40 0.09 24.60 0.00 0.00 19.67 99.07 6.85 3.87 1.93 0.03 4.03 0.00 0.00 12.25 6.00 3.87 1120 38.61 11.96 4.32 1.15 21.94 0.10 0.00 19.51 97.57 7.25 3.81 1.57 0.36 3.65 0.03 0.01 12.32 6.00 3.81 Ag/A–apfu of silver in triangular coordination; Cu/B–apfu f Cu1+ in tetrahedral coordination; Analyses are ordered according to increasing Ag content. Minerals 2019, 9, x FOR PEER REVIEW 23 of 45

authors have proposed a minimum content for freibergite of 4 apfu Ag [44,58], and a condition of Ag > Cu for argentotennantite (about 5 apfu Ag) [59]. On the basis of the results of crystal structure studies [58,60] and analyses of natural samples [61,62], Ag preferentially occupies the triangular A Mineralsposition2019 with, 9, 430 total content 6 apfu, and according to the present rules of mineralogical nomenclature25 of 47 [31], the boundary would be 3 apfu Ag [62].

(a) (b)

Agd Gn

Frg

Clh Frg 20  m 20  m

Figure 16. (a) Fractured mass of porous sphalerite (dark grey) contains ﬁssures ﬁlled by veinlets of freibergiteFigure 16.(medium (a) Fractured grey) mass with of exsolutions porous sphalerite of Se-rich (dark miargyrite grey) contains (15 wt.% fissures of Se, light filled grey) by veinlets and members of offreibergite galena–clausthalite (medium grey) solid with solution exsolutions (white) of from Se-rich Gal70–Claus30 miargyrite (15 (15 wt.% wt.% of of Se Se), light to Claus78–Gal22 grey) and (20members wt.% of of Se). galena (b) freibergite–clausthali (Frg)te solid in quartz solution of red(white) ore (ii)from containing Gal70–Claus30 inclusions (15 of wt.% clausthalite of Se) to (Clh, Minerals 2019, 9, x FOR PEER REVIEW 24 of 45 21.5%Claus7 of8– SeGal22) or members(20 wt.% of of Se). galena-clausthalite (b) freibergite (F solidrg) in solutionquartz of (Gn, red 14.2%ore (ii) of containing Se) and argyrodite inclusions (Agd,of 9.8%clausthalite of Se). Both(Clh, back-scattered21.5% of Se) or electronmembers (BSE) of galena images.-clausthalite solid solution (Gn, 14.2% of Se) and argyrodite (Agd, 9.8% of Se). Both back-scattered electron (BSE) images. 6.5 Two(a) groups of compositions were identified. The majority(b) of analyses (Table 16) represent 6.0 typical freibergite with more than 4 apfu of Ag. Its chemical composition is fairly monotonous with

regard5.5 to Fe/Zn and Sb/As ratios. Iron is always dominant, and As is not present, as is the case with

)

u f

allp sulfosalts in hypogene mineralization in Kutná Hora. Zonality phenomena are visible in some

a 5.0

(

grainsu quite profoundly, however, differing only moderately in terms of Ag/Cu ratio. Ag contents C were4.5 determined from 3.99 apfu (23.33 wt.%) to 7.25 apfu (38.61 wt.%) in freibergite, indicating that

the4.0 placement of Ag not only in the A position (up to 6 apfu), but also to a limited degree in the B position (up to 1.25 apfu) takes place. Freibergite with as much as 46.4 wt.% of Ag (8.93 apfu) was 3.5 described3.5 from4.0 the4.5 Rejzské5.0 pásmo5.5 Lode6.0 in6.5 the Kutná7.0 Hora ore district [18]. This phase corresponds to the newly approved mineral rozhdestvenskayaite [63]. Ag and Cu contents show an excellent Ag ( apfu) negative correlation (Figure 17a), which is in agreement with published results (e.g., [35,64,65]). In the caseFigureFigure of freibergite 17.17.( (aa)) GraphGraph below ofof Ag Ag6 apfu vs.vs. Cu CuAg, ((apfu apfuthe) )rest forfor freibergite;offreibergite the A position; ((bb)) graphgraph is filled ofof FeFevs. withvs. ZnZn copper. ((apfuapfu)) forf orThe freibergite.freibergite. B position, in addition to Ag contents (up to 0.40 apfu), is occupied by dominant Cu. In the C position, Fe (1.09– 2.02 apfuThe )second prevails group over ofZn analyses (0.03–0.98 correspond apfu), whichs to is members typical of at freibergite the boundary (Figure between 17b). Determinedfreibergite and Table 17. EPMA data for Ag-rich tetrahedrite/freibergite. AgAg/Cu-rich ratios tetrahedrite. show no This apparent member correlation is very withrare Fe/Znand was ratios. found In the only X position,in one sample the dominant of black Sb ore is in (i) as ana parthedral of analyses grains associated accompaniedwt.% with by galena, negligible freiesle As, notbenite, exceeding diaphorite, 0.09 apfu owyheeiteapfu (0.36Σ29 wt.%). atoms and Ag-excess fizélyite. Analyses Ag content Ag varies Cu from Fe 17.41 Zn to 18.48Sb wt. S%, Totalcorresponding Ag Cu to Fe 2.93 Zn to Sb 3.15 apfu S Ag, Ag/ AwhichCu/B is appreciably2047 17.41 less than 24.78 a typical 5.44 1.05 common 27.43 member 22.57 98.68 of the2.93 tetrahedrite 7.09 1.77 series, 0.29 which 4.10 12.80 is freibergite2.93 4.02on all lodes2045 of the17.84 Kutná 24.41 Hore 5.50 ore district. 1.08 27.64 The 22.65chemistry99.12 is 3.00similar 6.97 to 1.78freibergite 0.30 4.12 in the 12.81 respect3.00 that 3.97 iron prevails2046 over18.48 zinc, 23.81 no arsenic 5.35 1.08substitutes 27.40 22.24for antimony98.36 3.15 (Table 6.89 17) 1.76, and 0.30 the substitution 4.13 12.74 3.15of Se for 4.03 S is non-Agexistent/A–apfu,of although silver in triangular surrounding coordination; minerals Cu/B– containapfu of Cu as1+ inm tetrahedraluch as 1.1 coordination; wt.% of Se Analyses are ordered accordingA very interesting to increasing Agthing content. in the chemistry of freibergite and tetrahedrite is the fact that selenium does not enter the structure of freibergite, even if the grains of freibergite occur in a Se-rich environment,A very interesting which was thing documented in the chemistry both in ofblack freibergite ore (i) and and red tetrahedrite ore (ii). While is the all fact other that associated selenium doessulfosalts not enter take the in structureselenium ofmore freibergite, or less eagerly, even if the freibergite grains of remains freibergite Se occur-free. in a Se-rich environment, which was documented both in black ore (i) and red ore (ii). While all other associated sulfosalts take in selenium more or less eagerly, freibergiteTable 16. EPMA remains data Se-free. for freibergite.

wt.% apfu Ʃ29 atoms Analyses Ag Cu Fe Zn Sb As Se S Total Ag Cu Fe Zn Sb As Se S Ag/A Cu/B 2419 23.33 20.84 4.72 1.64 26.83 0.01 0.00 22.34 99.71 3.99 6.05 1.56 0.46 4.07 0.00 0.00 12.85 3.99 4.04 2547 26.62 18.16 5.07 1.64 26.72 0.03 0.13 22.68 101.04 4.54 5.25 1.67 0.46 4.03 0.01 0.03 13.00 4.54 3.79 2548 27.49 17.76 5.15 1.90 26.65 0.08 0.12 22.50 101.66 4.68 5.13 1.69 0.53 4.02 0.02 0.03 12.88 4.68 3.81 2549 27.83 17.54 4.95 1.72 26.74 0.00 0.13 22.42 101.32 4.76 5.10 1.64 0.49 4.06 0.01 0.03 12.91 4.76 3.86 2246 28.78 16.57 5.30 0.97 26.48 0.00 0.00 21.46 99.56 5.07 4.96 1.80 0.28 4.14 0.00 0.00 12.73 5.07 4.03 812 29.59 14.64 5.27 1.00 26.38 0.15 0.00 21.58 98.61 5.27 4.43 1.81 0.29 4.16 0.04 0.00 12.93 5.27 3.70 63 31.22 15.18 3.41 3.16 25.69 0.19 0.00 21.09 99.94 5.56 4.59 1.17 0.93 4.05 0.05 0.00 12.63 5.56 4.15 811 32.11 13.60 4.97 1.12 26.29 0.11 0.00 21.45 99.66 5.73 4.12 1.72 0.33 4.16 0.03 0.00 12.88 5.73 3.86 67 33.24 14.09 3.48 2.95 25.61 0.22 0.00 21.06 100.65 5.92 4.26 1.20 0.87 4.04 0.06 0.00 12.62 5.92 4.18 1461 33.55 13.78 5.01 1.07 25.59 0.11 0.00 20.91 100.01 6.02 4.19 1.74 0.32 4.07 0.03 0.00 12.62 6.00 4.19 42 33.87 13.64 3.56 2.63 25.63 0.21 0.00 20.52 100.06 6.12 4.19 1.24 0.78 4.11 0.05 0.00 12.48 6.00 4.19 36 34.60 13.45 3.75 2.30 25.69 0.23 0.00 20.65 100.67 6.22 4.11 1.30 0.68 4.09 0.06 0.00 12.50 6.00 4.11 2142 34.80 13.03 5.58 0.11 26.15 0.00 0.00 20.44 100.11 6.31 4.01 1.95 0.03 4.20 0.00 0.00 12.47 6.00 4.01 2140 36.99 12.32 5.40 0.09 24.60 0.00 0.00 19.67 99.07 6.85 3.87 1.93 0.03 4.03 0.00 0.00 12.25 6.00 3.87 1120 38.61 11.96 4.32 1.15 21.94 0.10 0.00 19.51 97.57 7.25 3.81 1.57 0.36 3.65 0.03 0.01 12.32 6.00 3.81 Ag/A–apfu of silver in triangular coordination; Cu/B–apfuof Cu1+ in tetrahedral coordination; Analyses are ordered according to increasing Ag content.

Table 17. EPMA data for Ag-rich tetrahedrite/freibergite.

wt.% apfu Ʃ29 atoms Analyses Ag Cu Fe Zn Sb S Total Ag Cu Fe Zn Sb S Ag/A Cu/B 2047 17.41 24.78 5.44 1.05 27.43 22.57 98.68 2.93 7.09 1.77 0.29 4.10 12.80 2.93 4.02 2045 17.84 24.41 5.50 1.08 27.64 22.65 99.12 3.00 6.97 1.78 0.30 4.12 12.81 3.00 3.97 2046 18.48 23.81 5.35 1.08 27.40 22.24 98.36 3.15 6.89 1.76 0.30 4.13 12.74 3.15 4.03 Ag/A–apfu of silver in triangular coordination; Cu/B–apfu of Cu1+ in tetrahedral coordination; Analyses are ordered according to increasing Ag content.

Minerals 2019, 9, x FOR PEER REVIEW 25 of 45

4.6. Ag-S, Ag-Se-S and Ag-Se Phases Minerals 2019, 9, 430 26 of 47 4.6.1. Acanthite, Ag2S Acanthite occurs as anhedral grains, fillings of other silver minerals, or veinlets 50 μm wide and 4.6.several Ag-S, hundred Ag-Se-S μm and long, Ag-Se associated Phases with pyrargyrite, allargentum and native silver (Figure 18a) in quartz–kutnohorite gangue of red ore (ii), where it originated from former argentite. It belongs to the 4.6.1. Acanthite, Ag S latest minerals in the2 association. This acanthite shows no selenium content. The second mode of occurrenceAcanthite of occurs acanthite as anhedralis drop-like grains, inclusions ﬁllings of of up other to 30 silver μm in minerals, pyrite of or red veinlets ore (ii), 50 whichµm wide are and severalcharacteristic hundred of µ increasedm long, associated Se content with with pyrargyrite, a continual transitionallargentum to aguandilarite native and silver naumannite (Figure 18a) in(Fi quartz–kutnohoritegure 18b–d). Occasionally, gangue inhomogeneous of red ore (ii), where grains it with originated oscillating from Se former content argentite. occur. Grains It belongs of toacanthite the latest richest minerals in selenium in the association.(with composition This close acanthite to aguilarite) shows noare seleniumusually under content. 10 x 10 The μm. second In modethe third of occurrence mode of occurrence of acanthite inclusions is drop-like of galena inclusions in pyrite of a upre partially to 30 µm re inplaced pyrite by of acanthite red ore, (ii),which which arehas characteristic a significant ofselenium increased content. Se content It is fairly with frequent a continual in red transition ore (ii), associated to aguilarite (but andnot naumannitein direct contact) with naumannite, clausthalite, argyrodite and aguilarite. (Figure 18b–d). Occasionally, inhomogeneous grains with oscillating Se content occur. Grains of Chemical composition of acanthite and corresponding chemical formulae are given in Table 18. acanthite richest in selenium (with composition close to aguilarite) are usually under 10 x 10 µm. In the Increased selenium contents are characteristic of the studied acanthite. In most cases, these are up to third mode of occurrence inclusions of galena in pyrite are partially replaced by acanthite, which has a 0.13 apfu, some very small grains have as much as 0.30 apfu (8.83 wt.%) (Figure 19). With regard to signiﬁcantthe small size selenium of grains, content. measured It is fairlyminor frequentcontents of in Cu, red Pb, ore Fe, (ii), Zn associated and Sb in (butsome not analytical in direct points contact) withare naumannite,probably influenced clausthalite, by surrounding argyrodite phases. and aguilarite.

(a) (b) Py Agu Slv* Aca Prg Slv Aca* Ala Gn Gn Ala Slv* Prg Slv* Prg Py Aca Ala Ala 200  m Aca 10  m

Aca

10  m Acs 30  m

Figure 18. (a) Mass and veinlets of allargentum (Ala) and Sb-rich silver (Slv*); veinlets thicken up to formFigure grains 18. ( ofa) pureMass Sb-freeand veinlets silver of (Slv). allargentum Pyragyrite (Ala) (Prg) and Sb forms-rich euhedralsilver (Slv* masses); veinlets and thicken acanthite up to (Aca) formsform veinletsgrains of and pure ﬁllings Sb-free around silver allargentum.(Slv). Pyragyrite Residues (Prg) forms of original euhedral galena masses (Gn) and are acanthite visible at (Ac thea) right sideforms of theveinlets grain, and the fillings mineral around is replaced allargentum. by acanthite. Residues (b of) aguilariteoriginal galena (Agu, (G 18n) wt.% are visible of Se) at replacing the galenaright (Gn)side of in the one grain, of plentiful the mineral galena is inclusions replaced by in acanthite. pyrite of red(b) oreaguilarite (ii). Some (Agu of, 18 the wt.% inclusions of Se) are replacing galena (Gn) in one of plentiful galena inclusions in pyrite of red ore (ii). Some of the fully replaced by Se-rich acanthite (Aca*, 4 wt.% of Se), which forms a nearly continuous solid solution from acanthite with no Se (Aca) through Se-rich acanthite to aguilarite and naumannite. (c) diversity of inclusions in pyrite of red ore (ii); the larger inclusion shows the replacement of galena (white) by acanthite (dark grey). The smaller inclusion below is argyrodite. d) large inclusion of Se-rich acanthite (Aca), inclusion of galena (Gn) and an inclusion of an unnamed Ag-Cu-S phase (Acs) in pyrite (Py) of red ore (ii). Minerals 2019, 9, 430 27 of 47

Chemical composition of acanthite and corresponding chemical formulae are given in Table 18. Increased selenium contents are characteristic of the studied acanthite. In most cases, these are up to 0.13 apfu, some very small grains have as much as 0.30 apfu (8.83 wt.%) (Figure 19). With regard to the small size of grains, measured minor contents of Cu, Pb, Fe, Zn and Sb in some analytical points are probably inﬂuenced by surrounding phases.

Table 18. EPMA data for acanthite.

wt.% apfu Σ3 Atoms Analyses Minerals 2019Ag, 9, x Cu FOR PEER Pb REVIEW Fe Cd Se S Cl Total Ag Cu Pb Fe Cd Se S26 Cl of 45 2814 86.85 0.13 0.00 0.00 0.00 0.00 12.16 0.00 99.39 2.03 0.01 0.00 0.00 0.00 0.00 0.96 0.01 2647 inclusions87.50 0.00 are fully0.05 0.42 replaced 0.17 by 1.03 Se-rich11.77 acanthite0.00 100.93 (Aca*, 2.03 4 wt.% 0.00 of 0.00 Se),0.02 which 0.00 forms 0.03 a 0.92 nearly 0.00 2646 continuous85.66 0.00 solid 0.09 solution 0.47 from 0.22 acanthite 1.21 11.06 with0.00 no Se98.71 (Aca) through2.04 0.00 Se-rich 0.00 acanthite 0.02 0.00 to aguilarite 0.04 0.89 and 0.00 2719 84.15 0.00 0.09 1.03 0.04 1.42 11.28 0.56 98.70 1.97 0.00 0.00 0.05 0.00 0.05 0.89 0.04 2623 naumannite.83.18 0.00 (c) 0.18 diversity 0.03 0.16of inclusions 3.64 12.36 in pyrite0.00 99.82 of red 1.91 ore (ii 0.00); the 0.00 larger 0.00 inclusion 0.00 0.11 shows 0.96 the 0.00 2579 replacement83.95 0.00 of galena 0.00 1.62 (white) 0.23 by 4.01 acanthite12.45 (da0.00rk grey). 102.31 The 1.87 smaller 0.00 inclusion 0.00 0.07 below 0.00 is argyrodite 0.12 0.93. d 0.00) 2596 large84.13 inclusion 0.05 of 0.05 Se-rich 0.64 acanthite 0.18 3.98 (Ac11.65a), inclusion0.00 100.67 of galena 1.94 (Gn 0.00) and 0.00 an inclusion 0.03 0.00 of 0.13an unnamed 0.90 0.00 2594 85.15 0.00 0.00 0.50 0.17 4.29 11.55 0.00 101.68 1.95 0.00 0.00 0.02 0.00 0.13 0.89 0.00 Ag-Cu-S phase (Acs) in pyrite (Py) of red ore (ii). 2601 79.66 0.33 0.77 0.05 0.06 8.83 8.29 0.00 98.27 1.97 0.01 0.01 0.00 0.00 0.30 0.69 0.00 Increased Fe and Pb contents are caused by surrounding galena or pyrite. Analyses are ordered according to increasing Se content.

acanthite aguilarite 30 naumannite

S (at. %)

0 0 5 10 15 20 25 30 35 Se (at. %)

FigureFigure 19. 19.Graph Graph Se vs.Se vs. S (at.%) S (at.% for) for acanthite, acanthit aguilaritee, aguilarite and and naumannite. naumannite.

4.6.2. Aguilarite, Ag4SeS Table 18. EPMA data for acanthite.

Aguilarite was conﬁrmed inwt.% one sample as a small anhedral grain 6 apfu4 µ mƩ3 inAtoms a galena inclusion Analyses × (25 µm across)Ag in pyriteCu ofPb redFe ore Cd (ii) (FigureSe 18S b);Cl aguilarite Total replacesAg Cu galena. Pb TheFe galenaCd Se inclusion S Cl was surrounded2814 86.85 by0.13 (but 0.00 not in0.00 direct 0.00 contact0.00 12.16 with) 0.00 smaller 99.39 inclusions—or 2.03 0.01 0.00 semi-euhedral 0.00 0.00 0.00 grains—of 0.96 0.01 acanthite2647 with87.50 variable 0.00 0.05 selenium 0.42 0.17 content 1.03 (from11.77 zero0.00 to100.93 4 wt.%). 2.03 Plentiful0.00 0.00 inclusions0.02 0.00 in0.03 pyrite 0.92 of0.00 2646 85.66 0.00 0.09 0.47 0.22 1.21 11.06 0.00 98.71 2.04 0.00 0.00 0.02 0.00 0.04 0.89 0.00 this sample2719 are84.15 formed—apart 0.00 0.09 1.03 from 0.04 predominant 1.42 11.28 0.56 galena 98.70 and 1.97 occasional 0.00 0.00 acanthite—by 0.05 0.00 0.05 argyrodite, 0.89 0.04 freibergite,2623 (Ge,Se)-rich83.18 0.00 0.18 acanthite, 0.03 0.16 clausthalite, 3.64 12.36 naumannite, 0.00 99.82 polybasite,1.91 0.00 pyrargyrite0.00 0.00 0.00 and 0.11 unnamed 0.96 0.00 Ag-Cu-S2579 phases.83.95 0.00 0.00 1.62 0.23 4.01 12.45 0.00 102.31 1.87 0.00 0.00 0.07 0.00 0.12 0.93 0.00 2596 84.13 0.05 0.05 0.64 0.18 3.98 11.65 0.00 100.67 1.94 0.00 0.00 0.03 0.00 0.13 0.90 0.00 2594 85.15 0.00 0.00 0.50 0.17 4.29 11.55 0.00 101.68 1.95 0.00 0.00 0.02 0.00 0.13 0.89 0.00 2601 79.66 0.33 0.77 0.05 0.06 8.83 8.29 0.00 98.27 1.97 0.01 0.01 0.00 0.00 0.30 0.69 0.00 Increased Fe and Pb contents are caused by surrounding galena or pyrite. Analyses are ordered according to increasing Se content.

4.6.2. Aguilarite, Ag4SeS Aguilarite was confirmed in one sample as a small anhedral grain 6 × 4 μm in a galena inclusion (25 μm across) in pyrite of red ore (ii) (Figure 18b); aguilarite replaces galena. The galena inclusion was surrounded by (but not in direct contact with) smaller inclusions—or semi-euhedral grains—of acanthite with variable selenium content (from zero to 4 wt.%). Plentiful inclusions in pyrite of this sample are formed—apart from predominant galena and occasional acanthite—by argyrodite, freibergite, (Ge,Se)-rich acanthite, clausthalite, naumannite, polybasite, pyrargyrite and unnamed Ag-Cu-S phases. The chemical composition of aguilarite exhibitss contents of Se in the range of 1.22–1.28 apfu (Table 19); with regard to the small size of grains, the measured minor contents of Pb and Fe are likely to be caused by surrounding phases. Aguilarite was defined by Bindi and Pingitore [66] as a

Minerals 2019, 9, 430 28 of 47

The chemical composition of aguilarite exhibitss contents of Se in the range of 1.22–1.28 apfu (Table 19); with regard to the small size of grains, the measured minor contents of Pb and Fe are likely to be caused by surrounding phases. Aguilarite was deﬁned by Bindi and Pingitore [66] as a member of the monoclinic solid solution acanthite–aguilarite with Se>S (more than 16.67 at.% Se), and at the same time, with Se contents below ca. 1.4 apfu (23.33 at.%), which represents a boundary for an orthorhombic S-rich naumannite (Figure 19).

Table 19. EPMA data for aguilarite.

wt.% apfu Σ6 Atoms Analyses Ag Pb Fe Cd Se S Total Ag Pb Fe Cd Se S 2577 74.02 1.64 1.84 0.20 17.59 4.65 99.94 3.75 0.04 0.18 0.01 1.22 0.79 2578 75.50 0.16 1.77 0.19 18.16 3.62 99.41 3.90 0.00 0.18 0.01 1.28 0.63 Elevated levels of Pb and Fe are caused by surrounding galena or pyrite.

The nomenclature of mineral phases along the Ag2S–Ag2Se join was published by Bindi and Pingitore [66]. They suggest that two distinct solid solution series could exist: monoclinic “acanthite-type” series including aguilarite in the range Ag2S–Ag2S0.4Se0.6, and an orthorhombic “naumannite-type” series between Ag2S0.3Se0.7–Ag2Se. The status of members with Se contents in the range 0.60–0.70 (or 1.2–1.4 for 6 apfu of aguilarite), which correspond to two-phase (monoclinic and orthorhombic) ﬁeld as was described by Pingitore et al. [67] or Pal’yanova et al. [68] is still under debate. According to Kullerud et al. [69], there are two possible explanations—presence of metastable cubic high-temperature phase or mixtures of two submicroscopic phases formed during cooling of homogenous cubic phase below 80 ◦C. Natural minerals with compositions related to this two-phase ﬁeld have also been reported [68,69]. The described aguilarite in Table 19 shows Se contents within the above-mentioned range, i.e., between 1.22 and 1.28 apfu, corresponding to 0.61 and 0.64 apfu, if calculated to 3 apfu. However, it is impossible to decide whether a metastable phase or a mixture of two submicroscopic phases is present.

4.6.3. Naumannite, Ag2Se Naumannite was found in four grains of three samples (9 point analyses). The mode of occurrence is very similar to aguilarite, i.e., in drop-like inclusions in massive pyrite of red ore (ii). In the ﬁrst sample, an inclusion of Se-rich miargyrite (8.7 wt% of Se) 100 µm across in pyrite contains an euhedral grain of naumannite 30 µm across and a semi-euhedral grain of clausthalite. Clausthalite and naumannite are not in direct contact and both minerals replace Se-rich miargyrite (Figure 20a). The second grain occurs in a 20 µm inclusion in pyrite formed by clausthalite, Se-rich stephanite (9.8 wt.% of Se) and naumannite. Clausthalite appears to be the earliest mineral, replaced by both stephanite and naumannite. In the third sample, an inclusion in pyrite 30 µm across is formed by Se-rich stephanite (9.1 wt.% of Se), which is replaced by naumannite. The shape of the inclusion is not drop-like, but rather euhedral, following the crystal shape of stephanite (Figure 14b). The fourth sample occurs in a galena inclusion of 140 µm in pyrite. An anhedral grain of naumannite 6 µm across replaces galena at one of its edges. Chemical composition of naumannite and corresponding chemical formulae are given in Table 20; the range of SSe 1 substitution in naumannite was determined to be 0.01–0.18 apfu (Figure 19). − With regard to the small size of grains, minor measured contents of Pb and Fe insome analytical points are probably inﬂuenced by surrounding phases. Minerals 2019, 9, 430 29 of 47 Minerals 2019, 9, x FOR PEER REVIEW 28 of 45

Nau Ste Py (a) Gn (b) Agd Frg

Gn Sp Clh Mia

Nau 20  m 20  m

Figure 20. (a) Larger inclusion in pyrite of red ore (ii): clausthalite (Clh, 19.6% of Se) and naumannite (Nau,Figure 23.9 20. wt.%(a) Larger of Se) inclusion replace selenianin pyrite miargyrite of red ore ( (Mia,ii): clausthalite 8.7 wt.% of(Cl Se).h, 19.6 Smaller% of Se) inclusion: and naumannite naumannite and(Nau selenian, 23.9 wt. stephanite% of Se) (Ste, replace 9.8 wt.% selenian of Se) miargyrite replace an (M intermediateia, 8.7 wt.% member of Se). of Smaller galena–clausthalite inclusion: solidnaumannite solution and (Gn, selenian 13.9% stephanite of Se, 5.3% (S ofte, S). 9.8 ( bwt.%) Se-rich of Se) argyrodite replace an (Agd,intermediate 4.9 wt.% member of Se) borderingof galena– on freibergiteclausthalite (Frg) solid in solution a galena (G (Gn)n, 13.9 inclusion% of Se, in 5.3% pyrite of S). of red(b) oreSe-rich (ii). arg Argyroditeyrodite (A andgd, freibergite4.9 wt.% of replace Se) galena,bordering both on minerals freibergite are (Frimmedrg) in a by galena pyrite (G (Py).n) inclusion in pyrite of red ore (ii). Argyrodite and freibergite replace galena, both minerals are rimmed by pyrite (Py).

Chemical composition of naumanniteTable 20. EPMA and corresponding data for naumannite. chemical formulae are given in Table 20; the range of SSe-1 substitution in naumannite was determined to be 0.01–0.18 apfu (Figure 19). wt.% apfu Σ3 atoms With regardAnalyses to the small size of grains, minor measured contents of Pb and Fe insome analytical points are probably Aginfluenc Pbed by Fe surrounding Cd Se phases. S Total Ag Pb Fe Cd Se S 2597 75.43 0.10 0.92 0.21 20.69 1.96 99.30 2.01 0.00 0.05 0.01 0.75 0.18 2696 74.20 0.00 1.06Table 0.17 20. EPMA 23.94 data 0.31 for naumannite 99.66 2.02. 0.00 0.06 0.00 0.89 0.03 2694 74.48 0.00 0.98 0.00 23.93 0.23 99.62 2.03 0.00 0.05 0.00 0.89 0.02 wt.% apfu Ʃ3 atoms Analyses2698 74.10 0.00 0.66 0.05 23.74 0.20 98.76 2.04 0.00 0.04 0.00 0.89 0.02 2697 74.06Ag Pb 0.00 Fe 0.56 Cd 0.05 Se 23.83 S 0.21Total 98.69 Ag 2.05 Pb 0.00Fe 0.03Cd 0.00Se 0.90S 0.02 26952597 75.4373.86 0.10 0.00 0.92 0.59 0.21 0.05 20.69 23.95 1.96 0.22 99.30 98.66 2.01 2.03 0.00 0.00 0.05 0.03 0.01 0.000.75 0.900.18 0.02 2696 74.20 0.00 1.06 0.17 23.94 0.31 99.66 2.02 0.00 0.06 0.00 0.89 0.03 4.7. Ag-Ge-S2694 and Ag-Cu-S74.48 0.00 sulﬁdes 0.98 0.00 23.93 0.23 99.62 2.03 0.00 0.05 0.00 0.89 0.02 2698 74.10 0.00 0.66 0.05 23.74 0.20 98.76 2.04 0.00 0.04 0.00 0.89 0.02 4.7.1. Argyrodite,2697 Ag74.068GeS 0.006 0.56 0.05 23.83 0.21 98.69 2.05 0.00 0.03 0.00 0.90 0.02 2695 73.86 0.00 0.59 0.05 23.95 0.22 98.66 2.03 0.00 0.03 0.00 0.90 0.02 Argyrodite was found in nine grains of three samples (16 point analyses). It occurs as individual anhedral grains up to 40 µm among bubble-shaped inclusions in pyrite of red ore (ii) (Figure 18c). 4.7. Ag-Ge-S and Ag-Cu-S sulfides It was also found in sphalerite as a 12 µm grain bordering on freibergite in a galena inclusion of 45 µm (Figure 20b). Argyrodite and freibergite replace galena and are rimmed by pyrite. The replacement 4.7.1. Argyrodite, Ag8GeS6 progresses from the clean-cut boundary with pyrite towards the centre of the galena inclusion, which is completelyArgyrodite enclosed was in found sphalerite; in nine in sphalerite grains of threeassociated samples with (16 miargyrite point analyses). and pyrite It (Figureoccurs as12 b); andindividual as inclusions anhedral in grains freibergite up to with40 μm remnants among bubble of members-shaped of inclusions galena-clausthalite in pyrite of solidred ore solution, (ii) (Figure 18c). It was also found in sphalerite as a 12 μm grain bordering on freibergite in a galena which are replaced by freibergite (Figure 16b). inclusion of 45 μm (Figure 20b). Argyrodite and freibergite replace galena and are rimmed by pyrite. Chemical analyses of argyrodite are complicated due to the small size of the grains; the measured The replacement progresses from the clean-cut boundary with pyrite towards the centre of the contents of Cu and Fe probably come from surrounding phases. Apart from major elements (Ag, Ge a galena inclusion, which is completely enclosed in sphalerite; in sphalerite associated with miargyrite S), signiﬁcant contents of Se up to 0.69 apfu (4.93 wt.%) were found. The chemical composition and pyrite (Figure 12b); and as inclusions in freibergite with remnants of members of and corresponding chemical formulae are given in Table 21. The discovery of germanium in the galena-clausthalite solid solution, which are replaced by freibergite (Figure 16b). geochemistryChemical of analyses the Kutn ofá Hora argyrodite ore district are complicated shows another due similarity to the small with size the of Freiberg the grains ore; district, the whichmeasured is the content type localitys of Cu for and argyrodite. Fe probably come from surrounding phases. Apart from major elements (Ag, Ge a S), significant contents of Se up to 0.69 apfu (4.93 wt.%) were found. The chemical composition and corresponding chemical formulae are given in Table 21. The discovery of

Minerals 2019, 9, 430 30 of 47

Table 21. EPMA data for argyrodite.

wt.% apfu Σ15 atoms Analyses Ag Cu Pb Fe Zn Ge Sb Se S Total Ag Cu Pb Fe Zn Ge Sb Se S 2614 78.19 0.00 0.11 1.84 0.00 5.66 0.13 0.10 17.72 103.84 7.80 0.01 0.01 0.35 0.00 0.838 0.01 0.01 5.94 2615 78.70 0.00 0.11 1.68 0.00 5.89 0.27 0.14 17.64 104.43 7.83 0.00 0.01 0.32 0.00 0.871 0.02 0.02 5.90 2616 73.91 0.00 1.11 1.40 0.00 6.95 0.60 0.70 17.05 101.81 7.57 0.00 0.06 0.28 0.00 1.06 0.05 0.10 5.87 2619 73.60 0.55 0.00 1.97 0.00 6.00 0.08 1.00 17.75 101.15 7.42 0.09 0.00 0.38 0.01 0.90 0.01 0.14 6.02 2707 72.59 0.54 0.25 2.31 0.00 5.53 0.00 1.03 18.04 100.63 7.31 0.09 0.01 0.45 0.01 0.83 0.00 0.14 6.12 2708 73.73 0.05 0.00 0.90 1.07 5.91 0.31 3.58 16.26 102.06 7.56 0.01 0.00 0.18 0.18 0.90 0.03 0.50 5.61 Elevated levels of Pb, Fe or Zn are caused by surrounding galena, pyrite or sphalerite. Analyses are ordered according to incereasing Se content. Minerals 2019, 9, x FOR PEER REVIEW 29 of 45

germanium in the geochemistry of the Kutná Hora ore district shows another similarity with the Freiberg ore district, which is the type locality for argyrodite.

Table 21. EPMA data for argyrodite.

wt.% apfu Ʃ15 atoms Analyses Ag Cu Pb Fe Zn Ge Sb Se S Total Ag Cu Pb Fe Zn Ge Sb Se S 2614 78.19 0.00 0.11 1.84 0.00 5.66 0.13 0.10 17.72 103.84 7.80 0.01 0.01 0.35 0.00 0.838 0.01 0.01 5.94 2615 78.70 0.00 0.11 1.68 0.00 5.89 0.27 0.14 17.64 104.43 7.83 0.00 0.01 0.32 0.00 0.871 0.02 0.02 5.90 2616 73.91 0.00 1.11 1.40 0.00 6.95 0.60 0.70 17.05 101.81 7.57 0.00 0.06 0.28 0.00 1.06 0.05 0.10 5.87 2619 73.60 0.55 0.00 1.97 0.00 6.00 0.08 1.00 17.75 101.15 7.42 0.09 0.00 0.38 0.01 0.90 0.01 0.14 6.02 2707 72.59 0.54 0.25 2.31 0.00 5.53 0.00 1.03 18.04 100.63 7.31 0.09 0.01 0.45 0.01 0.83 0.00 0.14 6.12 2708 73.73 0.05 0.00 0.90 1.07 5.91 0.31 3.58 16.26 102.06 7.56 0.01 0.00 0.18 0.18 0.90 0.03 0.50 5.61 Minerals 2019, 9, 430 31 of 47 Elevated levels of Pb, Fe or Zn are caused by surrounding galena, pyrite or sphalerite. Analyses are ordered according to incereasing Se content. 4.7.2. Ag-Cu-S Phases 4.7.2. Ag-Cu-S Phases Unnamed Ag-Cu-(S,Se) phases were found in ﬁve grains of three samples (23 point analyses) and Unnamed Ag-Cu-(S,Se) phases were found in five grains of three samples (23 point analyses) occur in a very similar way to argyrodite as individual inclusions in pyrite, not in contact with any and occur in a very similar way to argyrodite as individual inclusions in pyrite, not in contact with other mineral (Figures 18d and 21a). These phases were found as anhedral grains up to 50 30 µm any other mineral (Figures 18d and 21a). These phases were found as anhedral grains up to 50× × 30 among predominantly galena inclusions in pyrite in red ore (ii) (Figure 21b) and belong to the latest μm among predominantly galena inclusions in pyrite in red ore (ii) (Figure 21b) and belong to the minerals.latest minerals. Similar Similar to selenides to selenides and argyrodite,and argyrodite, these these grains grains are are enclosed enclosed in pyritein pyrite growth growth zones zones with plentifulwith plentiful bubble-shaped bubble-shaped inclusions. inclusions.

(a) Sp (b)

Acs Py

20  m 200  m

Figure 21. (a) Oval inclusion of unnamed Ag-Cu-(S,Se) phase (Acs) in pyrite (Py) of red ore (ii).Figure (b )21. bubble-shaped (a) Oval inclusion inclusions of unnamed in pyrite Ag-Cu of-(S,Se) red orephase (ii). (Acs) Plentiful in pyrite small (Py) inclusionsof red ore (ii). in pyrite(b) arebubble formed—apart-shaped inclusions from predominant in pyrite of galena red ore and ( occasionalii). Plentiful acanthite—by small inclusions argyrodite, in pyrite freibergite are (Ge,Se)-richformed—apart acanthite, from clausthalite, predominant naumannite, galena and polybasite, occasional pyrargyrite acanthite— andby unnamed argyrodite, Ag-Cu-S freibergite phases. Both(Ge,Se) back-scattered-rich acanthite, electron clausthalite, (BSE) images. naumannite, polybasite, pyrargyrite and unnamed Ag-Cu-S phases. Both back-scattered electron (BSE) images. A common feature of all analyses (Table 22) is that the metal/sulphur ratio is between 1.36 and 1.74, whileA all common known Ag-Cu-Sfeature of mineralsall analyses have (Table this ratio22) is equalthat the to 2.meta Higherl/sulphur contents ratio ofis Sbetween+ Se in 1.36 the anionicand part1.74, suggest while all a diknownfferent Ag structural-Cu-S minerals arrangement have this than ratio in known equal phasesto 2. Higher and/or contents a possible of S involvement + Se in the of Cuanionic2+ cation. part Thesuggest Ag and a different Cu contents structural with arrangement a clear negative than correlation in known phases(Figure and/or22a) were a possible observed. 2+ Theyinvolvement differ from of Cu known catio phasesn. The Ag in theand Ag-Cu-S Cu contents system with with a clear respect negative to: a)correlation the Ag/Cu (Figure ratio, 22a and) b) higherwere observed. contents ofThey Se indiffer the from anionic known part phases (Figure in 22 theb); Ag the-Cu contents-S system of minor with respect Se were to determined: a) the Ag/Cu to be ratio, and b) higher contents of Se in the anionic part (Figure 22b); the contents of minor Se were between 2 and 5 at.%. With regard to the rarity of Ag-Cu-S phases and to the minimal size of grains determined to be between 2 and 5 at.%. With regard to the rarity of Ag-Cu-S phases and to the whichMinerals does 2019, not9, x FOR rule PEER the influenceREVIEW of surrounding phases (especially contents of Fe and Zn), it cannot30 of 45 minimal size of grains which does not rule the influence of surrounding phases (especially contents be decided whether the measured points belong to new mineral phases. of Fe and Zn), it cannot be decided whether the measured points belong to new mineral phases.

35 44 stromeyerite 30 Anthony of Padua Anthony of Padua 42 (a) mckinstryite ideal composition (b) ideal composition 25

40 )

) 20 %

jalpaite

t a

( 38

a 15

(

S C 10 +

S 36 5 acanthite 34 acanthite jalpaite mckinstryite stromeyerite 0

32 30 35 40 45 50 55 60 65 70 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Ag (at. %) Cu/Ag FigureFigure 22. 22.(a )(a Graph) Graph Ag vs. Ag Cu vs. (at.%) Cu for(at. Ag-Cu-S%) for Ag mineral-Cu-S phases; mineral composition phases; composition range for mckinstryite range for aremckinstryite given from are [70 given]; (b) from graph [70 Cu]; /(Agb) g vs.raph S Cu/Ag+ Se (at.%) vs. S for+ Se Ag-Cu-S (at.%) for mineral; Ag-Cu- compositionS mineral; composition range for mckinstryiterange for mckinstryite are given fromare given [70]. from [70].

Table 22. EPMA data for unnamed Ag-Cu-S phases.

wt.% at.% Analyses Ag Cu Pb Fe Cd Zn Se S Total Ag Cu Pb Fe Cd Zn Se S 2653 78.57 3.64 0.00 0.67 0.09 0.00 2.17 13.85 98.99 57.88 4.55 0.01 0.95 0.06 0.00 2.18 34.33 2670 69.06 3.79 0.00 3.50 0.00 0.53 4.51 16.29 97.69 47.92 4.47 0.00 4.70 0.00 0.60 4.28 38.03 2664 75.73 4.91 0.19 0.88 0.17 0.20 4.76 12.72 99.57 55.82 6.14 0.07 1.26 0.12 0.25 4.80 31.53 2669 73.92 5.37 0.13 1.37 0.00 0.43 4.10 14.01 99.32 53.07 6.54 0.05 1.90 0.00 0.51 4.02 33.84 2668 74.92 5.41 0.11 1.46 0.05 0.41 4.39 14.14 100.88 53.03 6.50 0.04 2.00 0.03 0.48 4.24 33.66 2654 76.60 6.10 0.16 0.68 0.12 0.00 1.82 14.94 100.41 54.23 7.33 0.06 0.93 0.08 0.02 1.76 35.58 2649 72.54 7.46 0.19 0.84 0.15 0.00 2.60 15.09 98.86 51.23 8.94 0.07 1.14 0.10 0.04 2.51 35.85 2648 70.46 8.47 0.10 0.74 0.13 0.00 2.24 15.92 98.06 49.22 10.05 0.04 1.00 0.08 0.00 2.14 37.41 2650 68.35 8.89 0.19 1.07 0.08 0.00 3.51 15.18 97.26 48.25 10.65 0.07 1.46 0.05 0.00 3.38 36.04 2651 67.79 9.64 0.08 1.16 0.12 0.00 2.87 15.69 97.36 47.29 11.42 0.03 1.57 0.08 0.05 2.73 36.82 2734 60.24 15.60 0.22 1.45 0.10 0.00 2.21 18.11 97.92 39.15 17.21 0.07 1.82 0.06 0.00 1.96 39.59 2736 57.30 15.64 0.00 2.09 0.00 0.00 2.17 18.08 95.28 37.71 17.47 0.00 2.66 0.00 0.00 1.95 40.03 Elevated levels of Pb, Fe or Zn are caused by surrounding galena, pyrite or sphalerite. Analyses are ordered according to increasing Cu content.

4.8. Native Elements; Ag, Au Sulfides and Antimonides

4.8.1. Silver, Ag Native silver occurs as yellow-white metallic aggregates several mm in size in cavities of the kutnohorite-quartz gangue of Vein B (red ore (ii)), associated with other silver minerals, namely with miargyrite, pyrargyrite and freibergite, and also in ore (iii) associated with pyragyrite, miargyrite and diaphorite. Silver occurs in two varieties, which differ with regard to Sb content: hypogene (primary) Sb-rich silver (Table 23) and later (mobilized) pure Sb-free native silver (Table 24). Polished sections of Sb-free silver were found as grains up to 50 μm in veinlets of Sb-rich silver several hundreds μm long, which form rims of masses of allargentum (Figure 18a). This pure native silver contains only traces of Hg, As, Fe and Cl. The more abundant Sb-rich silver is associated with pyrargyrite, acanthite, allargentum and Sb-free silver. Contents of Sb in the range 0.01–0.03 apfu (1.3– 3.1 wt.%) are characteristic of this type of silver (Table 23, Figure 23).

Minerals 2019, 9, 430 32 of 47

Table 22. EPMA data for unnamed Ag-Cu-S phases.

4.8. Native Elements; Ag, Au Sulﬁdes and Antimonides

4.8.1. Silver, Ag Native silver occurs as yellow-white metallic aggregates several mm in size in cavities of the kutnohorite-quartz gangue of Vein B (red ore (ii)), associated with other silver minerals, namely with miargyrite, pyrargyrite and freibergite, and also in ore (iii) associated with pyragyrite, miargyrite and diaphorite. Silver occurs in two varieties, which diﬀer with regard to Sb content: hypogene (primary) Sb-rich silver (Table 23) and later (mobilized) pure Sb-free native silver (Table 24). Polished sections of Sb-free silver were found as grains up to 50 µm in veinlets of Sb-rich silver several hundreds µm long, which form rims of masses of allargentum (Figure 18a). This pure native silver contains only traces of Hg, As, Fe and Cl. The more abundant Sb-rich silver is associated with pyrargyrite, acanthite, allargentum and Sb-free silver. Contents of Sb in the range 0.01–0.03 apfu (1.3–3.1 wt.%) are characteristic of this type of silver (Table 23, Figure 23).

Table 23. EPMA data for Sb-rich silver.

wt.% apfu Σ1 Atom Analyses Ag Au Sb As Cl Total Ag Au Sb As Cl 2825 98.45 0.00 1.32 0.07 0.10 99.94 0.98 0.00 0.01 0.00 0.00 2827 98.49 0.00 1.89 0.00 0.11 100.49 0.98 0.00 0.02 0.00 0.00 2824 98.40 0.00 1.99 0.12 0.11 100.62 0.98 0.00 0.02 0.00 0.00 2813 98.16 0.00 2.10 0.11 0.11 100.48 0.97 0.00 0.02 0.00 0.00 2829 98.09 0.00 2.61 0.12 0.10 100.92 0.97 0.00 0.02 0.00 0.00 2844 97.16 0.00 2.73 0.05 0.10 100.04 0.97 0.00 0.02 0.00 0.00 2830 97.66 0.13 2.77 0.09 0.12 100.77 0.97 0.00 0.02 0.00 0.00 2838 97.17 0.09 2.92 0.09 0.13 100.40 0.97 0.00 0.03 0.00 0.00 2848 97.07 0.00 2.91 0.00 0.10 100.08 0.97 0.00 0.03 0.00 0.00 2833 97.53 0.00 2.99 0.15 0.12 100.79 0.97 0.00 0.03 0.00 0.00 2839 97.73 0.00 3.11 0.09 0.10 101.03 0.97 0.00 0.03 0.00 0.00 Analyses are ordered according to increasing Sb content.

Table 24. EPMA data for silver.

wt.% apfu Σ1 atom Analyses Ag Au Hg As Te Cl Total Ag Au Hg As Te Cl 2865 101.59 0.00 0.10 0.16 0.11 0.13 102.09 0.99 0.00 0.00 0.00 0.00 0.00 2866 101.61 0.06 0.00 0.07 0.12 0.11 101.97 0.99 0.00 0.00 0.00 0.00 0.00 2867 101.62 0.00 0.00 0.09 0.12 0.11 101.94 0.99 0.00 0.00 0.00 0.00 0.00 2868 101.53 0.00 0.20 0.10 0.10 0.13 102.06 0.99 0.00 0.00 0.00 0.00 0.00 2828 100.47 0.08 0.00 0.11 0.00 0.10 100.76 0.99 0.00 0.00 0.00 0.00 0.00

Interestingly, no native silver whatsoever occurs in plentiful bubble-like inclusions in pyrite—all are acanthite—with the exception of Au-rich silver (electrum).

4.8.2. Au-rich Silver (Ag,Au) Au-rich silver (electrum) was found in 10 grains of four samples (23 point analyses) of red ore (ii), enclosed in miargyrite (8 grains up to 10 µm; Figure 24a) or sphalerite (2 grains up to 42 µm; Figure 24b). The phase richest in gold (and also the largest grain) was found as an anhedral grain of 42 x 25 µm enclosed in Fe-rich sphalerite; it contains 0.42–0.44 apfu Au (56–57 wt.%) (Figure 24b). Contents of Au were determined to be within the range 0.17–0.35 apfu (28–48 wt.%). Traces of Hg, Sb and Te (Table 25) were also identiﬁed; the minor contents of S determined are probably caused by surrounding phases. Minerals 2019, 9, x FOR PEER REVIEW 31 of 45

Minerals 2019, 9, 430 34 of 47

30 Sb-rich silver 25 allargentum Au-rich dyscrazite 20 Minerals 2019, 9, x FOR PEER REVIEW 32 of 45

4.8.2. Au-rich15 Silver (Ag,Au)

Au-rich 10silver (electrum) was found in 10 grains of four samples (23 point analyses) of red ore

(ii), enclosedSb (at. %) in miargyrite (8 grains up to 10 μm; Figure 24a) or sphalerite (2 grains up to 42 μm; Figure 24b). The5 phase richest in gold (and also the largest grain) was found as an anhedral grain of 42 x 25 μm enclosed in Fe-rich sphalerite; it contains 0.42–0.44 apfu Au (56–57 wt.%) (Figure 24b). Contents of Au were determined to be within the range 0.17–0.35 apfu (28–48 wt.%). Traces of Hg, Sb 0 and Te (Table 25) were also identified; the minor contents of S determined are probably caused by surrounding phases. Members of70 the Au-Ag75 solid solution80 (electrum85) have been90 identified in95 the past from100 three lodes of Kutná Hora ore district on the basis of ore microscopy as allotriomorphic grains up 10 μm Ag+Au (at. %) enclosed in freibergite, pyrargyrite or miagyrite. Only one occurrence was analysed chemically by emission spectral analysisFigureFigure [71] 23.. 23.Graph Graph Ag Ag+ +Au Au vs. vs. SbSb (at.%)(at.%) forfor Ag-SbAg-Sb minerals.minerals.

(a) Interestingly, no native silver whatsoever (b) occurs in plentiful bubble-like inclusions in pyrite—all are acanthite—with the exception of Au-rich silver (electrum).

Table 23Mia. EPMA data for Sb-rich silver. wt.% apfu Ʃ1 Atom Analyses Ag Au Sb As Cl Total Ag Au Sb AsFrg Cl 2825 98.45 0.00 1.32 0.07 0.10 99.94 0.98 0.00 0.01 0.00 0.00 2827 98.49 0.00 1.89 0.00 0.11 100.49 0.98 0.00 0.02 0.00 0.00 Mia Sp 2824 98.40Ste 0.00 1.99 0.12 0.11 100.62 0.98 0.00 0.02 0.00 0.00 2813 98.16 0.00 2.10 0.11 0.11 100.48 0.97 0.00 0.02 0.00 0.00 282920  m 98.09 0.00 2.61 0.12 0.10 100.9220  m 0.97 0.00 0.02 0.00 0.00 2844 97.16 0.00 2.73 0.05 0.10 100.04 0.97 0.00 0.02 0.00 0.00

Figure2830 24. (a)97.66 Two grains0.13 of Au-rich2.77 silver0.09 (white) 0.12 in miargyrite100.77 (Mia)0.97 show 0.00 signs of0.02 crystal 0.00 shape. 0.00 VeinletsFigure2838 24. in ( miargyritea)97.17 Two grains are0.09 of ﬁlled Au-2.92rich in bysilver stephanite0.09 (white) 0.13 in (Ste); miargyrite100.40 (b) Au-rich (M ia)0.97 show silver signs (white)0.00 of crystal associated0.03 shape.0.00 with 0.00 freibergiteVeinlets2848 in (Frg) miargyrite97.07 in sphalerite are0.00 filled (Sp)2.91 in of by red stephanite0.00 ore (ii).0.10 This (Ste ) (semi-euhedral); (b100.08) Au-rich silver0.97 grain (white is0.00 the) associated largest0.03 individual with0.00 0.00 grainfreibergite2833 (40 mm (Fr97.53g) across) in sphalerite and0.00 also (Sp) a2.99 grainof red with 0.15ore (the ii). This highest0.12 (semi Au100.79-euhedral) content (56.00.97grain wt.%,is the0.00 largest i.e., 42.50.03 individual at.% 0.00 of Au). 0.00 Bothgrain2839 back-scattered (40 mm97.73 across) electron and0.00 also (BSE) a 3.11grain images. with0.09 the highest0.10 Au1 content01.03 (56.00.97 wt. %, 0.00i.e., 42.5 0.03at.% of Au).0.00 0.00 Both back-scattered electronAnalyses (BSE) are images. ordered according to increasing Sb content. Members of the Au-Ag solid solution (electrum) have been identiﬁed in the past from three lodes Table 25. EPMA data for Au-rich silver. of Kutná Hora ore district on the basisTable of ore 24 microscopy. EPMA data asfor allotriomorphic silver. grains up 10 µm enclosed in freibergite, pyrargyrite or miagyrite.wt.% Only one occurrence was analysedat% chemically by emission Analyses wt.% apfu Ʃ1 atom spectralAnalyses analysis Ag [71].Au Hg Sb Te S Total Ag Au Hg Sb Te S 2686 39.80Ag 56.50Au 0.00Hg 0.00 As 0.07 Te0.12 Cl96.49 Total55.90 Ag43.46 Au0.00 Hg0.00 As0.08 Te0.56 Cl 2689 40.82 56.41 0.00 0.00 0.12 0.08 97.42 56.62 42.85 0.00 0.00 0.14 0.36 4.8.3.2865 Uytenbogaardtite 101.59 0.00 Ag3 AuS0.102 0.16 0.11 0.13 102.09 0.99 0.00 0.00 0.00 0.00 0.00 2692 40.71 56.36 0.00 0.00 0.09 0.10 97.26 56.52 42.85 0.00 0.00 0.10 0.46 2866 101.61 0.06 0.00 0.07 0.12 0.11 101.97 0.99 0.00 0.00 0.00 0.00 0.00 2684Uytenbogaardtite 40.73 56.06 was 0.00 found 0.00 as one0.09 semi-euhedrall 0.08 96.95 grain56.76 9 642.79µm in0.00 massive 0.00 miargyrite0.10 0.35 of red 26852867 40.95101.62 56.31 0.00 0.000.00 0.00 0.09 0.10 0.12 0.08 0.1197.44 101.94 56.71 ×0.9942.71 0.000.00 0.000.00 0.000.12 0.000.38 0.00 ore (ii). The image in Figure 25a reveals that the grain contains minute inclusions of Au-rich silver 26832868 40.92101.53 55.84 0.00 0.000.20 0.00 0.10 0.06 0.10 0.08 0.1396.90 102.06 56.92 0.9942.54 0.000.00 0.000.00 0.000.07 0.000.36 0.00 (white2690 spots, one41.15 larger55.88 one 0.00 is visible 0.00 at the0.12 left0.12 edge 97.26 of the grain)56.94 with42.34 51.0 0.00 wt.% 0.02 of Au0.13 and 46.30.54 wt.% 2828 100.47 0.08 0.00 0.11 0.00 0.10 100.76 0.99 0.00 0.00 0.00 0.00 0.00 of Ag2691 (corresponding 41.41 55.53 to 35.70.00 at.% 0.00 Au), which0.09 are0.09 probably97.12 responsible57.34 42.11 for0.00 the lower0.00 sulphur0.10 0.41 content in the2688 measured 41.89 points55.68 of uytenbogaardtite.0.00 0.00 0.00 0.10 The top97.66 and 57.59 right edge41.92 of0.00 the grain0.00 displays0.03 0.46 a hem 2687 41.86 55.59 0.00 0.00 0.12 0.09 97.66 57.58 41.87 0.00 0.00 0.14 0.41 resembling2571 a48.58 reaction 47.84 product. 0.00 However,0.29 0.11 the 0.07 hem is96.90 formed 64.42 by uytenbogaardtite34.74 0.00 0.34 with 0.13 increased 0.33 Sb content,2572 a possible50.57 contamination45.87 0.20 0.36 from surrounding0.11 0.09 97.19 miargyrite. 66.10 32.83 0.14 0.41 0.13 0.39 2630 49.52 42.53 0.97 0.85 0.00 2.87 96.73 59.11 27.80 0.62 0.90 0.02 11.52 2627 56.48 39.40 0.52 0.83 0.15 0.76 98.14 69.06 26.38 0.34 0.90 0.16 3.13 2573 59.18 36.84 0.48 0.58 0.09 0.53 97.70 72.14 24.60 0.31 0.63 0.09 2.17 2574 59.43 36.62 0.00 0.74 0.10 0.57 97.46 72.35 24.41 0.00 0.80 0.11 2.33 2575 62.13 33.51 0.00 1.07 0.12 0.44 97.27 74.86 22.11 0.00 1.15 0.13 1.76 2749 61.73 32.85 0.00 1.20 0.00 0.69 96.48 73.96 21.56 0.00 1.28 0.00 2.77 2629 63.97 31.35 0.30 1.69 0.14 1.18 98.64 73.60 19.75 0.18 1.73 0.14 4.57 2628 66.73 27.60 0.28 2.19 0.18 1.76 98.73 74.11 16.78 0.17 2.15 0.17 6.57

Minerals 2019, 9, 430 35 of 47

Table 25. EPMA data for Au-rich silver.

wt.% at% Analyses Ag Au Hg Sb Te S Total Ag Au Hg Sb Te S Minerals 2019, 26869, x FOR PEER39.80 REVIEW 56.50 0.00 0.00 0.07 0.12 96.49 55.90 43.46 0.00 0.00 0.0833 of 450.56 2689 40.82 56.41 0.00 0.00 0.12 0.08 97.42 56.62 42.85 0.00 0.00 0.14 0.36 2692 40.71Analyses 56.36 are 0.00ordered 0.00 according 0.09 0.10to decreasing 97.26 Au 56.52 content. 42.85 0.00 0.00 0.10 0.46 2684 40.73 56.06 0.00 0.00 0.09 0.08 96.95 56.76 42.79 0.00 0.00 0.10 0.35

4.8.3. Uytenbogaardtite2685 40.95 Ag3AuS 56.312 0.00 0.00 0.10 0.08 97.44 56.71 42.71 0.00 0.00 0.12 0.38 2683 40.92 55.84 0.00 0.00 0.06 0.08 96.90 56.92 42.54 0.00 0.00 0.07 0.36 Uytenbogaardtite2690 41.15 was found 55.88 as 0.00 one semi 0.00-euhedrall 0.12 0.12 grain 97.26 9 × 56.946 μm in 42.34 massive 0.00 miargyrite 0.02 0.13 of red0.54 ore (ii). The2691 image in41.41 Figure 55.53 25a reveals 0.00 that 0.00 the 0.09 grain 0.09 contains 97.12 minute 57.34 inclusions 42.11 0.00 of Au 0.00-rich 0.10 silver0.41 (white spots,2688 one larger41.89 one is 55.68 visible 0.00 at the 0.00 left edge 0.00 of 0.10 the grain) 97.66 with 57.59 51.0 41.92 wt.% of 0.00 Au and 0.00 46.3 0.03 wt.%0.46 of Ag (corresponding2687 41.86 to 35.7 55.59 at.% Au) 0.00, which 0.00 are 0.12 probably 0.09 97.66responsible 57.58 for 41.87the lower 0.00 sulphur 0.00 0.14content0.41 2571 48.58 47.84 0.00 0.29 0.11 0.07 96.90 64.42 34.74 0.00 0.34 0.13 0.33 in the measured points of uytenbogaardtite. The top and right edge of the grain displays a hem 2572 50.57 45.87 0.20 0.36 0.11 0.09 97.19 66.10 32.83 0.14 0.41 0.13 0.39 resembling 2630a reaction49.52 product. 42.53 However, 0.97 0.85the hem 0.00 is 2.87formed 96.73 by uytenbogaardtite 59.11 27.80 0.62 with 0.90increased 0.02 Sb 11.52 content, a possible2627 contamination56.48 39.40 from 0.52 surrounding 0.83 0.15 miargyrite 0.76 98.14. 69.06 26.38 0.34 0.90 0.16 3.13 This is2573 the fir59.18st occurrence 36.84 0.48 of 0.58 uytenbogaardtite 0.09 0.53 97.70 in 72.14the Czech 24.60 Republic. 0.31 0.63 Recently, 0.09 2.17 uytenbogaardite2574 was59.43 described 36.62 from 0.00 the 0.74 selenium 0.10 0.57-rich 97.46 Au-Ag 72.35 mineralization 24.41 0.00 of the 0.80 Kremnica 0.11 2.33 Sb-Au-Ag epithermal2575 62.13 deposit, 33.51 Slovak 0.00ia [ 1.0772]. The 0.12 chemistry 0.44 97.27 of uytenbogaardtite 74.86 22.11 0.00 from 1.15 Kutná 0.13 Hora1.76 2749 61.73 32.85 0.00 1.20 0.00 0.69 96.48 73.96 21.56 0.00 1.28 0.00 2.77 (Table 26) shows a surplus of silver (3.16–3.33 apfu) and a deficit of sulphur (1.66–1.87 apfu) at all four 2629 63.97 31.35 0.30 1.69 0.14 1.18 98.64 73.60 19.75 0.18 1.73 0.14 4.57 analysed points.2628 Two66.73 analyses 27.60 show 0.28 a surplus 2.19 0.18of gold 1.76 (1.14 98.73 apfu), 74.11 and two 16.78 show 0.17 a deficit 2.15 (0.77 0.17 and6.57 0.87 apfu). We assume that the lower sulphur contents compared to stoichiometry are caused by the Analyses are ordered according to decreasing Au content. fact that the grain is, in fact, a submicroscopic intergrowth of uytenbogaardtite with Au-rich silver, which is visible on the BSE photograph (Figure 25a).

(a) (b)

Uyt Dys Dys Aca Uyt Aca

Mia

20  m 20  m

Figure 25. (a) Grain of uytenbogaardtite (Uyt) in miargyrite (Mia), inclusions of Au rich silver (white) Figure 25. (a) Grain of uytenbogaardtite (Uyt) in miargyrite (Mia), inclusions of Au rich silver (white) are visible at the left edge of the grain. (b) grain of Au-rich dyscrasite (Dys) in quartz of red ore (ii). are visible at the left edge of the grain. (b) grain of Au-rich dyscrasite (Dys) in quartz of red ore Au-rich dycrasite (3.7–4.1 wt.% of Au) replaces acanthite (Aca). Both back-scattered electron (BSE) (ii). Au-rich dycrasite (3.7–4.1 wt.% of Au) replaces acanthite (Aca). Both back-scattered electron images. (BSE) images. Table 26. EPMA data for uytenbogaardtite. This is the first occurrence of uytenbogaardtite in the Czech Republic. Recently, uytenbogaardite was described from the selenium-rich wt.% Au-Ag mineralization ofapfu the Ʃ6 Kremnica atoms Sb-Au-Ag epithermal deposit, SlovakiaAnalyses [72]. TheAg chemistry Au ofSb uytenbogaardtite S Total Ag from Au Kutn áSbHora S (Table 26) shows a surplus of silver (3.16–3.332951apfu ) and54.74 a deficit36.03 of0.61 sulphur 8.55 (1.66–1.87 99.93 3.16apfu ) at1.14 all four0.03 analysed1.66 points. Two analyses show a surplus2952 of gold 55.39 (1.14 apfu36.33), and0.64 two 8.61 show 100.97 a deficit 3.17 (0.77 1.14 and 0.03 0.87 1.66apfu ). We assume that the lower sulphur contents2955 59.93 compared 29.31 to0.74 stoichiometry 10.31 100.29 are 3.23 caused 0.87 by 0.04 the fact1.87 that the grain is, in fact, a submicroscopic2957 intergrowth 61.73 25.93 of uytenbogaardtite 0.85 10.27 98.79 with 3.33 Au-rich 0.77 silver,0.04 1.86 which is visible on the BSE photograph (Figure 25a). 4.8.4. Allargentum, Ag6Sb Allargentum (together with Sb-rich silver) is more abundant than native Sb-free silver in the hypogene mineralization. It is found as metallic white-yellow outgrowths, platelets or wire-like aggregates, usually up to several mm in size in the cavities of quartz–kutnohorite gangue of red ore (ii), associated with silver, pyrargyrite and miargyrite. In polished sections, it occurs as anhedral aggregates up to several hundred μm in size in miargyrite, associated with pyrargyrite and acanthite (Figure 18a).

Minerals 2019, 9, 430 36 of 47

Table 26. EPMA data for uytenbogaardtite.

wt.% apfu Σ6 atoms Analyses Ag Au Sb S Total Ag Au Sb S 2951 54.74 36.03 0.61 8.55 99.93 3.16 1.14 0.03 1.66 2952 55.39 36.33 0.64 8.61 100.97 3.17 1.14 0.03 1.66 2955 59.93 29.31 0.74 10.31 100.29 3.23 0.87 0.04 1.87 2957 61.73 25.93 0.85 10.27 98.79 3.33 0.77 0.04 1.86

4.8.4. Allargentum, Ag6Sb Allargentum (together with Sb-rich silver) is more abundant than native Sb-free silver in the hypogene mineralization. It is found as metallic white-yellow outgrowths, platelets or wire-like aggregates, usually up to several mm in size in the cavities of quartz–kutnohorite gangue of red ore (ii), associated with silver, pyrargyrite and miargyrite. In polished sections, it occurs as anhedral aggregates up to several hundred µm in size in miargyrite, associated with pyrargyrite and acanthite (Figure 18a). The chemical composition of allargentum is relatively uniform and is close to the ideal formula (Table 27, Figure 23); only traces of Cl were identiﬁed. The empirical formula for studied allargentum samples on the basis of 7 apfu (mean of 10 analyses) can be expressed as Ag5.95Sb1.02Cl0.02.

Table 27. EPMA data for allargentum.

wt.% apfu Σ7 atom Analyses Ag Au Sb As Cl Total Ag Au Sb As Cl 2812 84.28 0.00 16.46 0.05 0.09 100.88 5.94 0.00 1.03 0.01 0.02 2832 84.75 0.00 16.29 0.00 0.09 101.13 5.96 0.00 1.01 0.00 0.02 2841 84.74 0.00 16.49 0.00 0.10 101.33 5.94 0.00 1.02 0.00 0.02 2842 84.21 0.00 16.42 0.00 0.10 100.73 5.94 0.00 1.03 0.00 0.02 2843 84.60 0.09 16.32 0.06 0.08 101.15 5.95 0.00 1.02 0.01 0.02 2846 84.29 0.00 16.30 0.00 0.10 100.69 5.95 0.00 1.02 0.00 0.02 2847 84.54 0.00 16.34 0.00 0.08 100.96 5.95 0.00 1.02 0.00 0.02

4.8.5. Au-rich Dyscrasite (Ag,Au)3Sb Au-rich dyscrasite was found as one anhedral grain 60 x 30 µm in quartz, close to, but not in direct contact with, the massive miargyrite of red ore (ii) (Figure 25b). The chemical analysis of dyscrasite (Table 28) revealed interesting contents of Au in the range 0.08–0.10 apfu (3.65–4.11 wt.%). A small deﬁcit of Sb observed up to 0.08 apfu (Figure 23) corresponds to the ideal formula Ag3 + xSb1 x proposed for dyscrasite by Scott [73] on the basis of crystal − structure study.

Table 28. EPMA data for Au-rich dyscrasite.

wt.% apfu Σ4 atom Analyses Ag Au Sb Te S Total Ag Au Sb Te S 2760 70.84 3.65 24.66 0.13 0.07 99.35 2.98 0.08 0.92 0.00 0.01 2761 69.83 3.92 26.50 0.06 0.05 100.35 2.92 0.09 0.98 0.00 0.01 2762 67.81 4.11 26.98 0.00 0.21 99.10 2.87 0.10 1.01 0.00 0.03 Minerals 2019, 9, 430 37 of 47

4.9. Galena–Clausthalite Solid Solution

4.9.1. Galena Galena is a very frequent mineral in the Pb-rich black ore (i) from Vein B. It occurs as typical lead-grey cleavable grain aggregates several cm in size associated with other sulfides, occasionally as crystals in cavities. In polished sections, it was frequently found as the earliest mineral associated with boulangerite, freieslebenite, diaphorite, owyheeite, andorite group minerals, miargyrite and freibergite (Figure2a–c,e, Figure4, Figure5c,d, Figure8, Figure 10b, Figure 12a). It is also frequently found in the red ore type (ii) as plentiful bubble-shaped inclusions in pyrite (Figure 21b), and also as idiomorphic grains; usually, it is the earliest mineral. Very frequently, it occurs as filling of bubble-shaped inclusions in the pyrite of red ore (ii) (Figure 15a,b, Figure 16b, Figure 18b,c,d, Figure 20a,b, Figure 21a,b). It also occurs in ore (iii) (Figure2f). Increased Se contents (Table 29) were found only in small grains of galena (up to 20 µm across), associated with various Ag-Pb-Sb sulfosalts. Significantly increased Ag contents (up to 12.34 wt.%) were occasionally identified (34 points above 1 wt.% of Ag). These were found to be positively correlated with Sb contents (Figure 26a) and considerably higher than previously reported in the literature from this locality (0.10–0.21 wt.% [13,35]). Ag and Sb enter the structure of galena probably by the same mechanism as Ag and Bi in PbSSS, i.e., galena – matildite solid solution [74,75]. The maximum values of Ag and Sb in the galena grains are 0.22 apfu and 0.23 apfu. Sucha high degree of substitution was observed only in several grains and corresponds to the highest contents of PbSSS ([74,76,77]. In most studied galena grains, the contents of Ag do not exceed 0.12 apfu; a similar range of Ag + (Bi,Sb) 2Pb substations in PbS are known → SS from other occurrences around the world [23,74,75,77]. Measured contents of Se in galena (Table 29) are substantially higher than previously published data (0.14 wt.% Se [13]) and suggest an unlimited SeS 1 substitution in galena – clausthalite solid solution (Figure 26b); as mentioned before, higher Se − contents were determined for smaller aggregates of galena, usually not exceeding 20 µm.

Table 29. EPMA data for galena.

wt.% apfu Σ2 atom Analyses Ag Cu Pb Sb Se S Total Ag Cu Pb Sb Se S 2467 0.04 0.00 85.74 0.15 0.00 13.35 99.29 0.00 0.00 0.99 0.00 0.00 1.00 2013 0.09 0.05 85.80 0.13 0.19 13.49 99.75 0.00 0.00 0.98 0.00 0.01 1.00 857 0.00 0.00 85.81 0.19 0.44 13.59 100.04 0.00 0.00 0.98 0.00 0.01 1.00 2215 0.28 0.00 84.26 0.78 1.10 13.23 99.65 0.01 0.00 0.96 0.02 0.03 0.98 372 0.88 0.00 83.74 1.06 1.53 13.18 100.38 0.02 0.00 0.94 0.02 0.05 0.96 1264 0.21 0.00 83.85 0.28 2.57 12.38 99.29 0.00 0.00 0.97 0.01 0.08 0.93 2266 1.37 0.00 82.57 0.08 3.34 11.91 99.27 0.03 0.00 0.96 0.00 0.10 0.89 1494 0.08 0.00 84.30 0.16 3.64 11.92 100.11 0.00 0.00 0.98 0.00 0.11 0.90 23 0.13 0.31 84.51 0.09 3.83 12.03 100.90 0.00 0.01 0.97 0.00 0.12 0.89 2264 1.67 0.00 82.73 0.09 4.63 11.54 100.66 0.04 0.00 0.95 0.00 0.14 0.86 2315 1.29 0.00 82.87 0.07 5.10 10.84 100.17 0.03 0.00 0.98 0.00 0.16 0.82 22 0.20 0.31 83.63 0.08 5.38 11.12 100.72 0.00 0.01 0.97 0.00 0.16 0.84 2265 1.53 0.00 81.15 0.08 6.57 10.68 100.01 0.03 0.00 0.95 0.00 0.20 0.81 754 0.05 0.00 82.87 0.12 6.67 10.55 100.26 0.00 0.00 0.98 0.00 0.21 0.81 2314 1.01 0.00 82.32 0.06 6.82 9.98 100.19 0.02 0.00 0.98 0.00 0.21 0.77 1262 0.30 0.00 79.39 0.32 14.02 7.09 101.12 0.01 0.00 0.97 0.01 0.45 0.56 Analyses are ordered according to incereasing Se content. Minerals 2019, 9, x FOR PEER REVIEW 35 of 45

2Pb substations in PbSSS are known from other occurrences around the world [23,74,75,77]. Measured contents of Se in galena (Table 29) are substantially higher than previously published data (0.14 wt.% Se [13]) and suggest an unlimited SeS-1 substitution in galena – clausthalite solid solution (Figure 26b); as mentioned before, higher Se contents were determined for smaller aggregates of galena, usually not exceeding 20 μm. Minerals 2019, 9, 430 38 of 47

0.25 1.2

(a) (b) galena 1.0 0.20 clausthalite

0.8

) 0.15

)

a p

( 0.6 a

0.10

(

S S 0.05 0.4

galena 0.2 0.00 clausthalite

0.0 0.00 0.05 0.10 0.15 0.20 0.25 0.0 0.2 0.4 0.6 0.8 1.0 Minerals 2019, 9, x FOR PEER REVIEW 36 of 45 Ag ( apfu) Se ( apfu) (i) asFigure Figureinclusions 26. 26.( (aa )up) Graph Graph to 50 Ag Ag μm vs vs Sb inSb (apfu) (apfu)Se-free for for freieslebenite members members of of galena galena, which – – clausthalite clausthalite is replaced solid solid by solution. solution.clausthalite. ( b(b)) graph g raphGenerally, Se Se membersvsvs S S ( apfu( ofapfu ) the) for for clausthalitemembers members of of galena- galena – – clausthalite solidclausthalite solution solid solid solution.occurring solution. in black ore (i) are accompanied by 4.9.2.galena Clausthalite and Pb-Sb-(Ag) sulfosalts. Often a common trend is that smaller grains are Se-rich galena or clausthalite and larger grains of galenaTable are 29. generally EPMA data Se- forfree. galena . Clausthalite is the most frequently occurring selenide mineral. It was found in both black ore (i) It has to be noted that no sulphurwt.%-free clausthalite was found in anyapfu of theƩ2 atom measured samples. (Figure Analyses27) (two samples, 10 point analyses) and, even more often, in red ore (ii) (four samples, 10 point Sulphur contents inAg clausthalite Cu Pb (TableSb 30)Se range S between Total 0.10 Ag–0.50 Cu apfu Pb (4.87 Sb–6.28 Se wt. %)S ( Figure analyses). The mineral was found as anhedral grains in fractures in freibergite ﬁlled in by miargyrite 26b). An unlimited2467 0.04 miscibility 0.00 85.74 among 0.15 clausthalite 0.00 13.35 and galena99.29 was0.00 observed 0.00 0.99 in experimental0.00 0.00 1.00 studies in red ore (ii) (Figure 16a). This miargyrite shows increased amounts of selenium and belongs to the of phase 2013 relations 0.09 in this0.05 system85.80 0.13 at temperatures 0.19 13.49 above99.75 3000.00 ° C0.00 [78 –800.98]. The0.00 extrapolation0.01 1.00 of latest minerals of the association. Other clausthalite grains are observed in bubble-shaped inclusions in thermodynamic857 data0.00 for 0.00 end members85.81 0.19 enables 0.44 to13.59 envisage 100.04 the existence0.00 0.00 of0.98 a complete 0.00 0. solid01 1.00 solution pyrite of red ore (ii) (Figure 16b, Figure 20a) in association with Se-rich galena, accompanied by other PbSe–PbS2215 up to temperatures0.28 0.00 84.26 of about0.78 1001.10 °C 13.23[79,80 ]99.65. The existence0.01 0.00 of 0.96 a complete 0.02 0.03 isomorphous 0.98 minerals present in these inclusions (see aguilarite). Clausthalite was identiﬁed among compositions series PbS–372PbSe in0.88 natural 0.00 sample 83.74 s 1.06was described1.53 13.18 for 100.38the first 0.02 time 0.00 by Coleman0.94 0.02 [81 0.05], who 0.96 studied corresponding to the galena-clausthalite solid solution in black ore (i) as inclusions up to 50 µm in samples from1264 uranium0.21 0.00–vanadium 83.85 0.28 deposits 2.57 in12.38 the area99.29 of Colorado0.00 0.00 Plateau0.97 0.01, and 0.08 later 0.93, it was Se-free freieslebenite, which is replaced by clausthalite. Generally, members of the clausthalite-galena confirmed2266 by the research1.37 0.00 of 82.57samp les0.08 from 3.34 the deposits11.91 99.27 of Niederschlema 0.03 0.00 0.96–Alberoda 0.00 0.10 [82 ],0.89 Moldava solid solution occurring in black ore (i) are accompanied by galena and Pb-Sb-(Ag) sulfosalts. Often a [83] and Potůčky1494 [0.0884] in 0.00 Krušné 84.30 hory 0.16 Mountains 3.64 11.92 or Běstvina 100.11 in 0.00Železné 0.00 hory 0.98 Mountains 0.00 0.11 [ 850.90]. Unlike common trend is that smaller grains are Se-rich galena or clausthalite and larger grains of galena are coexisting galena,23 0.13clausthalite 0.31 84.51 contains 0.09 very 3.83 rarely 12.03 increased 100.90 contents0.00 0.01 of Ag0.97 (and 0.00 Sb) 0.12, not exceeding0.89 generally Se-free. 0.11 apfu or2264 0.04 apfu1.67, respectively 0.00 82.73 ( Figure0.09 284.63). In 11.54Table 30,100.66 the contents0.04 0.00 of Ag0.95 and 0.00 Sb are0.14 negligible. 0.86 2315 1.29 0.00 82.87 0.07 5.10 10.84 100.17 0.03 0.00 0.98 0.00 0.16 0.82 22 0.20 0.31 83.63 0.08 5.38 11.12 100.72 0.00 0.01 0.97 0.00 0.16 0.84 2265 1.53 0.00 81.15 0.08 6.57 10.68 100.01 0.03 0.00 0.95 0.00 0.20 0.81 754 0.05 0.00 82.87 0.12 6.67 10.55 100.26 0.00 0.00 0.98 0.00 0.21 0.81 2314 1.01 0.00 82.32 0.06 6.82 9.98 100.19 0.02 0.00 0.98 0.00 0.21 0.77 1262 0.30 0.00 79.39 0.32 14.02 7.09 101.12 0.01 0.00 0.97 0.01 0.45 0.56 Analyses are ordered according to incereasingClh Se content.

4.9.2. Clausthalite Frs Clausthalite is the most frequently occurring selenide mineral. It was found in both black ore (i) (Figure 27) (two samples, 10 pointGn analyses) and, even Clhmore often, in red ore (ii) (four samples, 10 point analyses). The mineral was found as anhedral grains in fractures in freibergite filled in by miargyrite in red ore (ii) (Figure 16a). This miargyrite shows increased amounts of selenium and belongs to the latest minerals of the association. Other clausthalite grains are observed in bubble-shaped inclusions in pyrite of red ore (ii) (Figure 16b, Figure 20a) in association with Se-rich galena, accompanied by other minerals present in these inclusions (see aguilarite). Clausthalite was identified among compositions corresponding to the galena-clausthalite solid solution in black ore Dia 50  m

Figure 27.27. The general succession in Se-enrichedSe-enriched black ore (i); clausthalite (Clh—16(Clh—16 wt.%wt.% of Se) and Se-richSe-rich galena (G (Gn,n, 2% Se) replaced by freieslebenite (F (Frs,rs, 0.3 0.3%% Se) and diaforite (D (Dia,ia, 3.5 3.5%% of of Se). Se). Back-scatteredBack-scattered electron (BSE) image.

Minerals 2019, 9, 430 39 of 47

It has to be noted that no sulphur-free clausthalite was found in any of the measured samples. Sulphur contents in clausthalite (Table 30) range between 0.10–0.50 apfu (4.87–6.28 wt.%) (Figure 26b). An unlimited miscibility among clausthalite and galena was observed in experimental studies of phase relations in this system at temperatures above 300 ◦C[78–80]. The extrapolation of thermodynamic data for end members enables to envisage the existence of a complete solid solution PbSe–PbS up to temperatures of about 100 ◦C[79,80]. The existence of a complete isomorphous series PbS–PbSe in natural samples was described for the ﬁrst time by Coleman [81], who studied samples from uranium–vanadium deposits in the area of Colorado Plateau, and later, it was conﬁrmed by the research of samples from the deposits of Niederschlema–Alberoda [82], Moldava [83] and Pot ˚uˇcky[84] in Krušné hory Mountains or Bˇestvinain Železné hory Mountains [85]. Unlike coexisting galena, clausthalite contains very rarely increased contents of Ag (and Sb), not exceeding 0.11 apfu or 0.04 apfu, respectively (Figure 28). In Table 30, the contents of Ag and Sb are negligible.

Table 30. EPMA data for clausthalite.

wt.% apfu Σ2 atom Analyses Ag Pb Zn Sb Se S Total Ag Pb Zn Sb Se S 303 0.19 77.35 0.50 0.09 16.35 6.36 100.83 0.00 0.94 0.02 0.00 0.52 0.50 239 0.05 78.52 0.41 0.06 16.32 5.90 101.26 0.00 0.97 0.02 0.00 0.53 0.47 1263 0.00 78.73 0.00 0.08 17.01 5.62 101.44 0.00 0.98 0.00 0.00 0.56 0.45 1255 0.05 78.43 0.00 0.10 17.60 5.66 101.83 0.00 0.98 0.00 0.00 0.58 0.43 1260 0.06 77.86 0.00 0.07 18.36 4.94 101.29 0.00 0.98 0.00 0.00 0.61 0.40 Minerals1261 2019, 0.00 9, x FOR76.47 PEER REVIEW0.00 0.08 18.74 4.87 100.16 0.00 0.97 0.00 0.00 0.62 0.4037 of 45 Analyses are ordered according to increasing Se content.

0.5

0.4 galena clausthalite

0.3

0.2

0.1

(Ag+Sb)/(Ag+Sb+Pb) 0.0

0.0 0.2 0.4 0.6 0.8 1.0 Se/(Se+S)

FigureFigure 28. 28Graph. Graph Se /Se/(Se(Se + S) + vs.S) vs (Ag. (Ag+ Sb) + Sb)/(Ag/(Ag + Sb+ Sb+ Pb)+ Pb) (apfu (apfu) for) for members members of of galena galena – clausthalite – clausthalite solidsolid solution. solution.

5. Discussion Table 30. EPMA data for clausthalite.

5.1. Succession of Crystalization wt.% apfu Ʃ2 atom Analyses The ore mineralizationAg Pb ofthe Zn whole Sb Kutn áSeHora S ore districtTotal originatedAg Pb inZn several Sb stages, Se separatedS by tectonic movements303 0.19 [2677.35]. Each 0.50 stage 0.09is 16.35 subdivided 6.36 100.83 into mineralization 0.00 0.94 0.02 sequences, 0.00 0.52 divided 0.50 by weaker tectonic239 events0.05 or by78.52 distinct 0.41 metasomatic 0.06 16.32 processes.5.90 101.26 The 0.00 similarity 0.97 of0.02 the Kutn0.00 á0.53Hora 0.47 [26] and 1263 0.00 78.73 0.00 0.08 17.01 5.62 101.44 0.00 0.98 0.00 0.00 0.56 0.45 1255 0.05 78.43 0.00 0.10 17.60 5.66 101.83 0.00 0.98 0.00 0.00 0.58 0.43 1260 0.06 77.86 0.00 0.07 18.36 4.94 101.29 0.00 0.98 0.00 0.00 0.61 0.40 1261 0.00 76.47 0.00 0.08 18.74 4.87 100.16 0.00 0.97 0.00 0.00 0.62 0.40 Analyses are ordered according to increasing Se content.

5. Discussion

5.1. Succession of Crystalization The ore mineralization of the whole Kutná Hora ore district originated in several stages, separated by tectonic movements [26]. Each stage is subdivided into mineralization sequences, divided by weaker tectonic events or by distinct metasomatic processes. The similarity of the Kutná Hora [26] and Freiberg [29] districts leads us to compare the nomenclature of the succession schemes in both districts (Table 31).

Table 31. Comparative table of mineral sequences in Kutná Hora and Freiberg.

Kutná Hora Freiberg [29] Stage Sequence Ore type Sequence Ia. Fe-As Fe-As I. Ib. Zn-Sn-Cu-Fe Zn-Sn-Cu Ic. 1stcarbonate ´kb´ IIa. Pb-Ag Pb-Ag II. IIb.2nd carbonate IIIa. Ag-Sb ´eb´, ´eq´ Ag-Sb III. IIIb. Sb-Fe IV. quartz–pyrite–calcite

Minerals 2019, 9, 430 40 of 47

Freiberg [29] districts leads us to compare the nomenclature of the succession schemes in both districts (Table 31).

Table 31. Comparative table of mineral sequences in Kutná Hora and Freiberg.

Kutná Hora Freiberg [29] Stage Sequence Ore type Sequence Ia. Fe-As Fe-As I. Ib. Zn-Sn-Cu-Fe Zn-Sn-Cu Ic. 1stcarbonate ‘kb’ IIa. Pb-Ag Pb-Ag II. IIb.2nd carbonate IIIa. Ag-Sb ‘eb’, ‘eq’ Ag-Sb III. IIIb. Sb-Fe IV. quartz–pyrite–calcite ‘kb’—“kiesig-blendige Bleierzformation”; ‘eb’; ‘eq’—“edle Braunspatformation”; “edle Quarzformation”.

The veins of northern “pyrite-rich” lodes are characterized by the presence of the first two stages: Fe-As sequence (Ia); Zn-Sn-Cu-Fe sequence (Ib) and Pb-Ag sequence (IIa). Also present in northern lodes—though on smaller scale than in the south—is the later third stage: Ag-Sb sequence (IIIa) and Sb-Fe sequence (IIIb). On the contrary, the southern “silver-rich” lodes are characterized by a much smaller presence of the first two stages and a complete absence of Sn in Ib sequence and an almost exclusive representation of the stage III with frequent kutnohorite in gangue [8,86]. The Oselské pásmo Lode, including the newly studied mineralization of Anthony of Padua mine (this paper) are a typical example of southern "silver-rich" lodes and the origin of this ore mineralization is bound to the youngest Ag–Sb sequence (IIIa). On the basis of published data as well as of new study (this paper), it was possible to single out several fundamental types (kinds) of ore: the Pb-rich black ore (i); the Ag-rich red ore (ii) in quartz–kutnohorite gangue; the Ag-rich ore (iii) in quarz gangue (see Section 4.1). Several hundred BSE images of seventy measured polished sections were examined and conclusions regarding associations and parageneses drawn. The succession of minerals in individual samples was determined where possible. Several trends, general features and repeated patterns were observed. The general succession follows the trend from Pb-rich phases to Pb-poorer (Ag-richer) phases. The earliest mineral in all three types of ore is galena. (i) black ore—Pb-rich black ore in quartz with the general succession: galena – boulangerite (– jamesonite) – owyheeite – fizélyite – Ag-excess fizélyite – andorite IV – andorite VI – freieslebenite – diaphorite – miargyrite – freibergite. This belongs to Ag-Sb sequence IIIa, corresponding in the Freiberg succession scheme to Ag-Sb sequence of ‘eb’ ore type or the transitional ore type between ‘kb’ and ‘eb’, with an overprint of Se mineralization. (ii) red ore—the Ag-rich red ore in kutnohorite + quartz. Three succession patterns are noticeable: one is galena – diaphorite – freibergite – miargyrite – pyragyrite – stephanite – polybasite – acanthite; the second is galena – allargentum – pyrargyrite – Sb-rich silver – silver (Sb-free) – acanthite; and the third is galena – freibergite – argyrodite – unnamed Ag-Cu-S phases (a reverse trend of argyrodite being replaced by freibergite was occasionally observed). Concerning the position of gold alloys in the succession, the only observable examples are: Au-rich silver – uytenbogaardtite – miargyrite; sphalerite – Au-rich silver – freibergite; and Au-rich silver – miargyrite. This corresponds to Ag-Sb sequence IIIa, with overprints of Se, Ge and Au mineralizations, corresponding to ‘eb’ ore type, and the Ag-Sb sequence in Freiberg. (iii) Ag-rich ore in milky quartz consists of crystals in cavities, bands and lenses of Ag minerals (mainly miargyrite), base sulfides are scarce. The usual succession is: galena – freieslebenite – diaphorite – freibergite – miargyrite – pyrargyrite/pyrostilpnite – stephanite – acanthite. It belongs to Ag-Sb Minerals 2019, 9, 430 41 of 47 sequence III, with a weaker overprint of Se mineralization; corresponds to ‘eq’ ore type, Ag-Sb sequence in Freiberg. The second, parallel succession scheme progresses from Se-free through Se-poor to Se-rich phases, such as: galena – members of galena - clausthalite solid solution – clausthalite; miargyrite – Se-rich miargyrite; acanthite – aguilarite – naumannite etc. The mutual relationship between the three ores (i, ii and iii) is difficult to assess with regard to their occurrences in different veins. The authors of this article are of the opinion that the Pb-rich black ore (i) is the earliest of the three, followed by (ii) and (iii).

5.2. Discussion of the Formation Conditions The Kutná Hora ore district is considered a typical example of postmagmatic sulfide base-metal mineralization of late Variscan age (Early Permian; [87]), analogous to the ‘kb + eb’ ore types (mineralizations) of Freiberg in Saxony, Germany [28,29]. Silver minerals (‘eb’, the Ag-Sb sequence in Freiberg) in the whole Kutná Hora ore district occur mostly on independent younger structures (Ag-Sb sequence IIIa) within the vein system; marked differences between the southern (dominant stage III (i.e.’eb’ and ‘eq’ ore type), weaker stage II (‘kb’) and northern lodes (dominant stage I and II (‘kb’), weaker stage III (‘eq’) are primarily caused by a different geological (petrological, tectonic) structure of both parts [26]. Bernard and Žák [88] suggested that mineralization of Kutná Hora ore district generally originated at high temperatures (430 80 C + ‘kb’ stage); younger parts of the ± ◦ mineralization (‘eb/eq’ stage) were colder (< 190 ◦C; [89]). According to Seifert and Sandmann [29] an analogous Ag-Sb mineralization from the Freiberg district (‘eb’ ore type) originated at temperatures between 300–120 ◦C. They also mention possible mineralogical and geochemical similarities to epithermal-style Ag-Au mineralization [90,91]. The similarity of the studied Ag-Sb mineralization from southern “silver-rich” lodes of the Kutná Hora ore district with the ‘eb’ ore type of the Freiberg district is highlighted by the newly discovered germanium-bearing mineral argyrodite and by Au and Se presence in Kutná Hora correlating with the argyrodite occurrence and locally increased Au and Se contents in ‘eb’ ores of the Freiberg district [29]. The character of the discovered selenium mineralization (i.e., increased selenium contents in Ag- and Pb-Sb sulfosalts, the occurrence of minerals of galena – clausthalite solid solution, and Se-rich acanthite, aguilarite and naumannite) indicates the formation from hydrothermal fluids with f O2 slightly above or close to hematite - magnetite buffer and the f Se2/f S2 ratio close to unity. The presence of minerals of galena – clausthalite solid solution shows that the upper values of the f Se2/f S2 ratio were more likely controlled by the galena – clausthalite buffer, which is still close to unity [92,93]. The occurrence of naumannite and acanthite which was deposited together with silver and Ag-sulfosalts requires conditions close to the native Ag-naumannite + acanthite invariant point [93,94]. Together with observed minerals of the galena – clausthalite solid solution it is possible to define a f Se2range of 23 to 26 and a f range of 21 to 22, respectively [93,94]. These values correspond very well − − S2 − − with conditions published for selenide-bearing Au-Ag epithermal deposits by Simon et al. [93]. Although Kutná Hora ore district including Anthony of Padua mine is not a volcanic low-sulfidation epithermal deposit, the studied mineralization shows many similar features. The source of selenium is probably in the bodies of (meta)ultrabasic rocks (serpentinites) frequently found by boreholes in southern “silver” lodes both south of town, as well as in its historic centre. The topomineral properties of these rocks may enable to pre-concentrate selenium which was released into hydrothermal fluids during tectonic events. The amphibolite from the quarry of Markovice, 10 km SE of Kutná Hora, known up to now only for the occurrence of zeolites, was recently found to contain selenides, tellurides and native tellurium [95,96]. The origin of selenides and tellurides from this locality is assumed to be related to (meta)ultrabasic rocks cutting through amphibolite rocks. A similar situation is also known from the northern part of the Kongsberg deposit, Norway [97]. Minerals 2019, 9, 430 42 of 47

6. Conclusions (1) The previously unknown selenium mineralization (clausthalite, naumannite, aguilarite) and increased selenium contents in Ag- and Pb-Sb sulfosalts were determined in hydrothermal ore veins from Anthony of Padua mine near Poliˇcany. These veins are part of the Oselské pásmo Lode, one of the southern “silver-rich” lodes of the historic Kutná Hora ore district. The determined contents of Se in Ag- and Pb-Sb sulfosalts belong to the highest ever found worldwide. (2) A suite of more than twenty silver minerals were determined in samples from Anthony of Padua mine: Ag-Pb-Sb sulfosalts (Ag-excess fizélyite, fizélyite, andorite IV, andorite VI, diaphorite, freieslebenite, owyheeite), Ag-Sb-(Cu)-sulfosalts (miargyrite, pyrargyrite, stephanite, polybasite, freibergite, Ag-rich tetrahedrite), Ag-sulfides and selenides (acanthite, aguilarite, naumannite, argyrodite), native elements, Ag, Au sulfides and antimonides (native silver and its Sb- or Au-rich variety, allargentum, Au-rich dyscrasite, uytenbogaardtite) and unnamed Ag-poor Ag-Pb-Sb sulfosalts and Ag-Cu-S mineral phases. The Pb-Sb sulfosalts (boulangerite, semseyite, jamesonite), and lead sulfide and selenide (members of galena – clausthalite solid solution) were also determined. (3) Three kinds of ore were identified in studied samples: Pb-rich black ore (i), Ag-rich red ore (ii) in quartz–kutnohorite gangue, and Ag-rich ore (iii) in quarz gangue without sulfides. The general succession follows the trend from Pb-rich phases to Pb-poorer and Ag-richer phases. The earliest mineral is galena. The general successions scheme is for the Pb-rich black ore (i) as follows: galena – boulangerite (– jamesonite) – owyheeite – fizélyite – Ag-exces fizélyite – andorite IV – andorite VI – freieslebenite – diaphorite – miargyrite – freibergite. For the Ag-rich red ore (ii) and ore (iii), the most prominent pattern is galena – diaphorite – freibergite – miargyrite – pyragyrite – stephanite – polybasite – acanthite. The parallel succession scheme progresses from Se-poor to Se-rich phases, for example, galena – members of galena - clausthalite solid solution – clausthalite; miargyrite – Se-rich miargyrite; acanthite – aguilarite – naumannite; etc. (4) The observed Ag-rich mineral association provides an insight into the character of exploited ore on historic silver-rich lodes from the south of the Kutná Hora ore district, such as Oselské pásmo Lode and Roveˇnské pásmo Lode, which were the main silver deposits of Kutná Hora district in the 14th century. It is evident that silver minerals such as miargyrite and freibergite were the main sources of silver, and not the alleged low contents of Ag in base-metal sulfides (most frequently as inclusions of Ag minerals) like on northern lodes. (5) The origin of economic silver mineralization of southern “silver-rich” lodes of the Kutná Hora district is bound primarily to the youngest Ag-Sb sequence IIIa, corresponding to the Ag-Sb sequence of the ‘eb/eq’ ore types in the Freiberg succession scheme. Earlier stages with base sulfide sequences, e.g., Zn-Sn-Cu-Fe sequence Ib and Pb-Ag sequence IIa, corresponding to the ‘kb ‘ore type, which are abundantly present on lodes in the northern part of the Kutná Hora district, are much less developed (Pb-Ag sequence IIa) or missing (Zn-Sn-Cu-Fe sequence Ib). The described Ag-Sb mineralization of the Kutná Hora ore district is analogous to the Ag-Sb sequence of the younger ‘eb/eq’ ore type (mineralization) of the Freiberg district, Saxony, Germany, including a local minority presence of Ge, Au and Se minerals. (6) The ore mineralization of the Kutná Hora ore district is a typical example of postmagmatic sulfide hydrothermal mineralization of late Variscan age. The Ag-rich mineralization of southern “silver-rich” lodes originated under temperatures significantly lower (< 190 ◦C) than the earlier mineralization of northern lodes (430 80 C); lower temperatures (300–120 C) are stated in the literature for the origin ± ◦ ◦ of the analogous ‘eb’ mineralization (ore type) of the Freiberg district, Saxony, Germany. (7) The association found between selenides and other Se-bearing mineral phases indicates hydrothermal fluids with fO2 slightly above or close to hematite-magnetite buffer and af Se2/f S2 ratio close than unity: the ranges are -23 to -26 and -21 to -22 for f Se2 and f S2, respectively. These values correspond very well to conditions published for selenide-bearing Au-Ag epithermal deposits. The mineralogical and geochemical similarities of the entirety of the latest ‘eb’ ore type (mineralization) of the Freiberg ore district and the low-sulfidation epithermal-style Ag–Au mineralization have been published previously. Minerals 2019, 9, 430 43 of 47

(8) The source of seleniumin Kutná Hora is probably related to the bodies of (meta)ultrabasics (serpentinites) frequently found by boreholes in southern “silver” lodes both south of town and in its historic centre. The topomineral properties of these rocks may enable to pre-concentrate selenium which was released into hydrothermal ﬂuids during tectonic events.

Author Contributions: R.P. collected samples and processed EMPA data. R.P., J.S. and V.Š. interpreted the results, V.Š. carried out ore microscopy and succession studies; R.P. and J.S. wrote the paper. Funding: The research was financially supported by the Czech Science Foundation (GACRˇ project 15-18917S) to RP and by the Ministry of Culture of the Czech Republic (long-term project DKRVO 2019–2023/1.I.a; National Museum, 00023272) for JS, and Project Nr. 528006 of the Czech Geological Service of the Czech Ministry of Environment for VS. Acknowledgments: The authors thank Ivo Macek and ZdenˇekDolníˇcek(National Museum, Prague), Martin Racek and Radim Jedliˇcka(Charles University, Prague) for their kind cooperation with EPMA analyses. Anonymous referees, as well as guest editor are acknowledged for comments and suggestions that helped greatly to improve the manuscript. Conflicts of Interest: The authors declare no conflict of interest.

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