Rem: Revista Escola de Minas ISSN: 0370-4467 [email protected] Universidade Federal de Brasil

Dias Menezes Filho, Luiz Alberto; de Sá Carneiro Chaves, Mario Luiz; Heinis Dias, Coralie; Atencio, Daniel Recent discoveries in the ,Taquaral, and Medina fields, northeastern , Brazil Rem: Revista Escola de Minas, vol. 69, núm. 3, julio-septiembre, 2016, pp. 301-307 Universidade Federal de Ouro Preto Ouro Preto, Brasil

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GeosciencesGeociências Recent mineral discoveries in the Coronel Murta,Taquaral, and Medina pegmatite fields, northeastern http://dx.doi.org/10.1590/0370-44672015690087 Minas Gerais, Brazil Luiz Alberto Dias Menezes Filho Abstract (in memoriam) The occurrence of five rare in the Eastern Brazilian Pegmatite Province,

Mario Luiz de Sá Carneiro Chaves northeastern Minas Gerais, is described and discussed: bergslagite [CaBe(AsO4)(OH)]

Professor Titular from the Manoel Fonseca mine, Coronel Murta county; herderite [CaBe(PO4)F] from

Universidade Federal de Minas Gerais - UFMG the Funil mine, Medina county; lithiophosphate [Li3PO4] from the Cachoeira mine,

Instituto de Geociências Araçuaí/ counties; lithiotantite [Li(Ta,Nb)3O8] from the Murundu mine, Itinga

Belo Horizonte - Minas Gerais – Brasil county; and kosnarite [KZr2(PO4)3] from Mario Pinto mine, Itinga county. The host [email protected] of these minerals, with their respective main chemical and/or mineralogical features are also presented. As a consequence of such discoveries, Raman spectra for Coralie Heinis Dias lithiotantite and lithiophosphate were made available, and refinement Doutoranda for lithiotantite was performed. Universidade Federal de Minas Gerais - UFMG Instituto de Geociências Keywords: pegmatites, mineralogical discoveries, Minas Gerais State. - Minas Gerais – Brasil [email protected]

Daniel Atencio Professor Associado Universidade de São Paulo – USP Instituto de Geociência São Paulo – São Paulo – Brasil [email protected]

1. Introduction

The Eastern Brazilian Pegmatite almost 42% of all Brazilian type minerals. chemical characterization and geological Province is very important for its pro- Nevertheless, mineralogical studies context, represent the aim of this paper. duction of industrial minerals (, about deposits from this wide region are All the minerals were also confirmed by feldspar, mica and ), as well as for still scarce. In recent years, the authors of X-ray diffractometry. For EMP analysis gemology and mineralogical collection the present work have been attempting to (Microscopy Center – UFMG), samples purposes. Several pegmatite districts are reverse the scenario of minor importance were mounted on polished sections and known, and two of them ( and given to Brazilian minerals. A research line metalized with C. For bergslagite and Araçuaí) are focused in this paper (Figure devoted to the identification of possibly herderite, the following standards were

1). Pegmatites from this province are char- new mineral species, through detailed used: fluorite – F, apatite – P2O5, FeAs2 – acterized by the presence of rare minerals, studies on the mineralogy of deposits con- As2O5, and apatite – CaO; for kosnarite, some of them are Brazilian type minerals: sidered promising has enabled the finding the standards used were: MgO – MgO,

28 of the 67 minerals described for the of rare minerals. magnetite – FeO, monazite – P2O5, Al2O3 first time from Brazilian samples were The description of five of such – Al2O3, HfSiO4 – HfO2, ZrSiO4 – ZrO2, originally found in this large region, i.e. findings with their mineralogical and ZrSiO4 – SiO2, and sanidine – K2O.

2. Bergslagite [CaBe(AsO4)(OH)] from the Manoel Fonseca mine (Olho d’Água farm, Coronel Murta county)

Originally described in Sweden by Hansen et al. (1984), this mineral quarry, Franconia, Bavaria), Norway (Langban mine, Bergslagen region) was found later in Germany (Fuchs (Tennvatn pegmatite, Nordland), Italy

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(Mt. Cervandone), and Switzerland droxylherderite [CaBe(PO4)(OH)], and – Figure 2a) where it was found is lo- (Fallota, Fianel mine, and Cavradi can be colorless, whitish or greyish, cated around 15 km north of Coronel gorge). It is monoclinic, isostructural with a vitreous luster. The Manoel Murta town, in the pegmatite field of

with herderite [CaBe(PO4)F] and hy- Fonseca mine (805130E / 8170236N the same name.

Figure 1 Schematic geographic map showing the eight main pegmatite districts in the Eastern Brazilian Pegmatite Province, emphasizing the focused ones in Northeastern Minas Gerais, the Coronel Murta, Taquaral and Medina fields. Towns: BH, Belo Horizonte (capital of the State); GV, Governador Valadares; DI, Diamantina; AR, Araçuaí.

Biotite schist and quartzite of ly active, is 4 m thick. The wall zone Two quartz crystals with about 15 the Macaúbas Group predominate extends to the contact with the coun- cm length were collected at this pegma- in the region, in the vicinity of the try rock, is fine-grained, and consists tite; their faces are coated with several contact with a relatively small peg- predominantly of pertitic microcline small white crystals, about 3 mm each matoid granite stock. The pegmatite with intercalations of quartz (graphic (Figure 2b). Electron microprobe anal- with about 8 m thick, and more than texture), and small amounts of musco- yses have identified a bergslagite core, 100 m long is intruded in the schist, vite and schorl. The intermediate zone bordered by a herderite layer about 0.1 and is concordant with the wall rock is constituted by microcline (thicker mm thick (Table 1). Figure 2c shows foliation (approximate direction and grains), quartz, muscovite, albite, and a scanning electron microscopy image dip, N65°E/40°NE). It is a zoned schorl. The quartz core is discontinu- by backscattered electrons of one of body, composed by lower and upper ous and can reach 1 m thickness or those crystals. The empirical formulae

domains, separated by 1 m of schist. more; decimetric replacement bodies are: bergslargite Ca1.06Be1.00(As0.96P0.04)

The upper domain (NE), from where of albite occur around it, where mil- Σ1.00O4.00[(OH)0.53F0.33O0.14]Σ1.00, and the studied samples came, produced limetric crystals of apatite with a light herderite Ca0.95Be1.00(P0.92As0.08)

topaz, and is nowadays abandoned. green-bluish to brown color are abun- Σ1.00O4.00[F0.48(OH)0.42]Σ0.90. The lower domain (SW), current- dant, together with milky herderite.

(a) (b)

(c) Figure 2 (a) Geology of the Coronel Murta pegmatite field, with its main pegmatites. MF: Manoel Fonseca mine (modified from Pedrosa-Soares, 1996). (b) Bergslagite on quartz. (c) Backscattered electron image of the crystal analyzed according Table 1, showing a bergslagite core (lighter phase) and a herderite rim. 302 REM: Int. Eng. J., Ouro Preto, 69(3), 301-307, jul. sep. | 2016 Luiz Alberto Dias Menezes Filho et al.

Table 1 Sample F P O As O CaO BeO(**) H O(***) Total O≡F(****) Total2 Electron microprobe 2 5 2 5 2 analyses of bergslagite (be) and her- drite (he) from the Manoel Fonseca 26B1-be (*) 2.97 1.49 52.16 28.17 11.83 2.26 98.88 (-1.25) 97.63 mine (wt %). (*) 20 spots average; (**) BeO content calculated for 1 Be 26B1-he (*) 5.54 39.64 5.30 32.05 15.15 2.26 99.94 (-2.33) 97.61 apfu ; (***) H2O calculated for charge neutrality; (****) oxygen equivalent.

3. Herderite [CaBe(PO4)F] from the Funil mine (Medina county)

Herderite was originally described yellow fluorapatite is a common acces- the first one in the world with confirmed by Haidinger (1828), at the Sauberg mine, sory mineral in the replacement bodies. provenience; that mine would then be- Saxony, Germany; hydroxylherderite, This pegmatite is zoned, quite weathered, come the mineral’s type locality, and that

CaBe(PO4)(OH), was found by Penfield with thickness about 3 m and is directed sample’s crystal structure would be stud- (1894) at the Paris county, Maine, USA. to E-W. Near to the surface, the body ied. However, at the same time Harlow & There are conflicting interpretations in is subvertical, while in greater depths it Hawthorne (2008) described and studied the literature, and it is common to refer dips approximately 40ºS. The wall zone the crystal structure of herderite from to any of those two minerals by the ge- exhibits thinner grains, and the inter- Mogok, Myanmar (with 8.7%). Those neric name herderite. Over the past two mediate zone is composed by weathered authors mention, in that paper, another decades, all attempts of confirmation of microcline, with quartz grains and biotite occurrence, from Yichung, China (7.25% the existence of herderite had failed, and sheets, both measuring few centimeters. F), found as an inclusion within a topaz Back & Mandarino (2008) emphasized: Albite-rich zones wholly kaolinized, with crystal. Thus the studied specimen rep- “Herderite (a doubtful species), sym- several centimeters width, are considered resents the world’s third occurrence (7B1 metry unknown, no chemical data with to be guides for aquamarine search. The grain from Table 2). F>OH are known, may form a series quartz core is discontinuous and has Another small group of crystals with hydroxylherderite…”. The mineral normally few decimeters of thickness. was discovered in 2011 (26A grains is monoclinic, and can be colourless, pale The analyzed herderite samples from Table 2), with the same aspects as yellow, beige, greenish-white or purplish, came from a set of euhedral and cen- the previous one, including faces coated with a vitreous luster. timetric crystals, with a greenish grey with thin schorl crystals. The fluorine The Funil mine (238222E / color, and were collected near the hang- content in those samples is even higher, 8204543N) is located in the Medina peg- ing wall, where, in the 1990’s important according to chemical analyses on two matite field (Figure 3A), which is included topaz findings occurred. Topaz is F-rich different crystal fragments, one removed in the Pedra Azul pegmatite district, ac- and tends to crystallize upwards in peg- from the crystal rim and the other close cording to Pedrosa-Soares et al. (2011). matite bodies due to thermal – gravita- to the core; no significant differences Pegmatite bodies from this district are tional diffusion of volatile components between them can be observed. The internal to proximal (marginal) source (Pedrosa-Soares et al., 2011). Topaz empirical formulae for herderite are: granite; they are generally small to me- materializes the higher fluorine content Ca0.95Be1.00(PO4)1.00[F0.56(OH)0.36]Σ0.92 dium (up to 5 m thick) and homogeneous, concentrated in residual melts, and thus (sample 7B1), and Ca0.96Be1.00(PO4)1.00 biotite-rich and tourmaline-poor or -free; it coexists with F-enriched terms of herd- [F0.69(OH)0.23]Σ0.92 (sample 26A). Data lithium minerals are also absent. Depos- erite – hydroxylherderite series. In August for Medina herderite was published by its from that area aim the extraction of 2009, a sample of herderite (Table 2) RRUFF database R100064 (free access gemologic beryl and topaz; green and from the Funil mine was supposed to be through www.rruff.info).

Sample F P O CaO BeO(*) H O(**) Total O≡F(***) Total2 Table 2 2 5 2 Electron microprobe analyses of herderite from the Funil mine (wt.%). Samples: 7B1, 4 spots 7B1 6.59 44.09 33.19 15.55 2.02 101.44 (-2.77) 98.67 average; 26A, 40 spots average; (*) BeO content calculated for 1 Be apfu; (**) calculated for charge neutrality; 26A 8.16 43.97 33.38 15.52 1.29 102.32 (-3.44) 98.88 (***) oxygen equivalent.

4. Lithiophosphate [Li3PO4] from the Cachoeira mine (Barreiro, Araçuaí/Itinga counties)

This mineral was first described in Manitoba), USA (Foote mine, Cleveland, be colourless or slightly rose-coloured. the Voroya tundra, Kola peninsula, Rus- North Carolina and Tip Top mine, The Cachoeira mine is operated by sia, in the 1950’s (Matias & Bondareva, Custer, South Dakota) and Morroco the Brazilian Lithium Company (CBL) 1957). Some other occurrences were (Mrirat pegmatite, Marrakesh). It is or- since 1990, aiming underground extrac- later reported in Canada (Tanco mine, thorhombic, has a vitreous luster and can tion of spodumene as lithium ore, and

REM: Int. Eng. J., Ouro Preto, 69(3), 301-307, jul. sep. | 2016 303 Recent mineral discoveries in the Coronel Murta,Taquaral, and Medina pegmatite fields, northeastern Minas Gerais, Brazil

is considered the most important of this by a swarm of pegmatites, generally Spodumene crystals are light green, kind in the country. It is located at the tabular and with lateral continuities up tabular along (110) and can reach up to margins of the Piauí river, which locally to hundreds meters. They are homoge- 1.5 m in length, but their average size limits the border between Itinga and neous and have rare replacement bod- ranges, in general, between 10 and 20 Araçuaí counties. Currently it is being ies. Their minimum thickness ranges cm. Most of the bodies are parallel to operated in its western front, in the lat- between 3 and 4 m, and the essential the foliation of the surrounding schist ter county (mine office center: 189721E mineralogy is composed of microcline, (N50°E/ 45ºNW), although one of the / 8142540N – Figure 3b). spodumene, albite, quartz and mus- most important is discordant, directed According to Romeiro & Pedrosa- covite. Accessory minerals are monte- to NE with subhorizontal to subvertical Soares (2005), the deposit is constituted brasite, beryl and niobium-tantalates. SE-dipping.

(a) (b)

Figure 3 (a) Geology of the Medina pegmatite field. FU = Funil mine (modified from Pinto, 2008). (b) Geology of the Taquaral pegmatite field, highlighting the Cachoeira (MC), Murundu (MU) and Mario Pinto (MP) pegmatites (modified from Paeset al., 2008).

Even if the several pegmatite of rare minerals. Such research led to prismatic, striated crystals, isolated bodies that occur in that area have the identification of the lithiophos- or in druses. All of those minerals are an apparently simple mineralogical phate species, in crystals with size and partially covered by submillimetric behavior, a systematic study has been perfection undoubtedly never reported spheres of fluorapatite. conducted in small replacement bodies before (Figure 4a). The mineral oc- Data for lithiophosphate from the (generally with a diameter of less than curs in cavities filled by albite, quartz, Cachoeira mine is now available in the 5 cm) aiming the possible localization muscovite and cookeite, as millimetric RRUFF database R100092.

(a) (b)

Figure 4 (a)Photo of prismatic crystal of lithiophosphate in albite with cookeite from the Cachoeira mine. (b) Detailed image of perfect lithiotantite crystals from the Murundu pegmatite.

5. Lithiotantite [Li(Ta,Nb)3O8] from the Murundu mine (Jenipapo, Itinga county)

Lithiotantite was first described in Manono granitic pegmatite, Democratic previously described by Cassedanne & the tantalum deposit of Ognevka, Ka- Republic of Congo, but its structure was Cassedanne (1980, 1985), concerning zakhstan, by Voloshin et al. (1983). A still unknown by the time of the finding its main minerals and geological aspects, second occurrence at the Ungursai tanta- at the Murundu mine, which is the fifth although its location was imprecise (now lum Deposit, Irtysh River, Kalba Range, one worldwide. Unlike the first descrip- defined: 192974E / 8156119N – Figure Eastern Kazakhstan Province (Shyghys tion (transparent, colorless), the mineral 3b), besides it was erroneously designated Qazaqstan Oblysy; Vostochno-Kazakh- is dark red (Figure 4b).It is monoclinic, in as “Mulundu”. It is constituted by a large stanskaya Oblast') was quoted by Pekov tabular and twinned crystals upon milky pegmatite body, subhorizontal, hosted in (1998). The third and fourth occurrences quartz, or associated with reddish brown the Salinas schist, with well-defined inter- were described by Uher et al. (2008) at the prismatic tantalite, and black cassiterite. nal zoning and a thick quartz core. The Urubu mine, Itinga, Minas Gerais, and the The Murundu pegmatite has been pegmatite was operated at the surface until 304 REM: Int. Eng. J., Ouro Preto, 69(3), 301-307, jul. sep. | 2016 Luiz Alberto Dias Menezes Filho et al.

the end of the 1980’s, mainly for industrial or cassiterite and/or columbite-tantalite Σ1.00(Ta 2.18Nb0.79Sn0.03)Σ3.00O8.00. The crystal feldspar, beryl and montebrasite. Cavities were found in replacement bodies around structure refinement was obtained by rich in well-formed quartz crystals and the core. Menezes Filho et al. (2012). As for lithio- yellow muscovite were frequently found in Electron microprobe analyses of phosphate, the University of Arizona has the core and commercialized as collection lithiotantite from Murundu pegmatite incorporated a new page about the Raman pieces; several small pockets containing are presented in Table 3. The empiri- spectrum of this mineral in its RRUFF gemological elbaite (green and blue) and/ cal formula is: (Li0.96Mn0.02Fe0.01Na0.01) database R100165.

Table 3 Sample Ta O Nb O TiO Na O MnO FeO SnO Li O Total Electron microprobe 2 5 2 5 2 2 2 2 analyses of lithiotantite from the Murundu mine, 6 spots average 14A 78.80 17.24 0.00 0.07 0.23 0.07 0.86 2.35 99.62

(wt %; total iron as FeO; Li2O calculated).

6. Kosnarite [KZr2(PO4)3] from the Mario Pinto mine (Jenipapo, Itinga county)

Kosnarite was first described by field), in the same State. Kosnarite from the x 10 m. The pegmatite is medium-grained Brownfieldet al. (1993), from samples of Jorge pegmatite, also in the Jenipapo area, size, composed essentially by muscovite two very close North-American localities, is quoted in Mindat (http://www.mindat. and feldspar on both sides of an irregular Mount Mica quarry and Black Mountain org/locdetailed-205524.html). Kosnarite quartz core, with small pockets in the vi- pegmatite, Oxford county, Maine. Shortly from Jenipapo is recorded in the RRUFF cinity, and some rose quartz crystals. The afterwards, the mineral was identified in database (R060250). This occurrence is of maximum thickness of the body varies Wyche Proof, Victoria, Australia (Birch et great importance due to its superior size around 15 m. al., 1994). In both countries, studied speci- and high quality. Kosnarite occurs as beautiful mil- mens are extremely small, submillimetric, The Mario Pinto mine (193465E / limetric druses, beige or vivid to pale showing trigonal (pseudocubic) crystals; 8154143N – Figure 3b) is also located in yellow, with pseudo-octahedral crystals color ranges from pale blue to blue-green the Taquaral pegmatite field, 2.5 km south up to 2 mm generally upon albite (cleave- to nearly colorless, with a vitreous luster. of Murundu pegmatite. It is a zoned peg- landite), and associated or not with brown Hyrsl et al. (2003) described kosnarite matite hosted in biotite schist of the Sali- spherulites of zanazziite (Figures 5a, b, samples from the Limoeiro mine, Virgem nas Formation, that strikes N40° and dips and c). Electron microprobe analyses of da Lapa, and Frost et al. (2012) studied vertically. The workings have uncovered kosnarite from the Mario Pinto mine are material from Jenipapo area (Taquaral the pegmatite for an extension of about 30 presented in Table 4.

(a) (b)

Figure 5 (a) Beige kosnarite druse from the Mario Pinto pegmatite. (b) Detailed aspect of the (c) central part of the pseudo- octahedral crystals from “photo A”. (c)Another sample, showing the rare vivid yellow color of the kosnarite aggregate on albite.

Sample ZrO2 P2O5 K2O HfO2 SiO2 MgO FeO Al2O3 Total

Kos1 46.46 42.02 9.04 2.33 0.05 0.00 0.00 0.00 99.90

Kos2 45.96 41.56 9.51 2.11 0.00 0.05 0.01 0.02 99.21

Kos3 46.90 41.72 9.17 2.28 0.00 0.01 0.02 0.00 100.10

Table 4 Kos4 45.64 42.28 9.07 2.97 0.04 0.00 0.08 0.04 100.10 Electron microprobe analyses of kosnarite from the Kos5 47.51 40.52 9.39 2.08 0.04 0.06 0.00 0.01 99.59 Mario Pinto mine (wt %; total iron as FeO). REM: Int. Eng. J., Ouro Preto, 69(3), 301-307, jul. sep. | 2016 305 Recent mineral discoveries in the Coronel Murta,Taquaral, and Medina pegmatite fields, northeastern Minas Gerais, Brazil

7. Concluding remarks

The Eastern Brazilian Pegmatite species; Langban iron and manganese brought advances in this respect, result- Province can still be considered very mine, Sweden – 71 species; Tsumeb ing in the recent findings of new pegma- poorly studied, besides the 28 new lead and copper mine, Namibia – 71 tite minerals, such as carlosbarbosaite minerals found in it. As example, some species, Katanga mining district, Re- (Atencio et al., 2012), cesarferreiraite mines or mining districts globally public of Congo – 65 species. Still in (Scholz et al., 2014) and correianevesite known, where many more minerals this regard, in a country with very little (Chukanov et al., 2014). Likewise, find- have already been described, can be mining tradition as Italy, 312 miner- ings reported in this paper (bergslagite, cited: Khibiny alkaline massif, Kola als have been described. However, herderite, lithiophosphate, lithiotantite peninsula, Russia – 116 species; Frank- the mineralogical research line being and kosnarite) also highlight this im- lin zinc mine, New Jersey, USA – 71 developed by this group of authors has portant initiative.

8. References

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an Pictures. Moscow, 1998. 369 p. PENFIELD, S.L. On the crystallization of herderite. American Journal of Science, v. 147, p. 329-339, 1894. PINTO, C.P. Folha SE.24-V-A-II . Programa Geologia do Brasil, Carta Geológica – Escala 1:100.000. CPRM-Serviço Geológico do Brasil, Belo Horizon- te, 2008, 1 map. ROMEIRO, J.C.P., PEDROSA-SOARES, A.C. Controle do minério de espodumênio em pegmatitos da mina da Cachoeira, Araçuaí, MG. Geonomos, v. 13, p. 75-81, 2005. 2+ 3+ SCHOLZ, R. et alii. Césarferreiraite, Fe Fe2 (AsO4)2(OH2).8H2O, from Eduardo mine, Conselheiro Pena, Minas Gerais, Brazil: second arsenate in the laueite mine- ral group. American Mineralogist, v. 99, p. 607-611, 2014. 2+ 2+ UHER, P. et alii. Foordite-thoreaulite, Sn Nb2O6–Sn Ta 2O6: compositional varia- tions and alteration products. European Journal of Mineralogy, v. 20, p. 501-516, 2008.

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Received: 1 June 2015 - Accepted: 28 April 2016.

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