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Member of the Aenigmatite Group

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MINERALOGlCA.L MAGAZINE, MARCH 1978, YOLo 42, PP. 129-32 Welshite, Ca2Mg4Fe3+Sb5~02[Si4Be2018J, a new member of the aenigmatite group PAUL B. MOORE Department of the Geophysical Sciences, The University of Chicago, Chicago, Illinois 60637, U.S.A. SUMMARY. Welshite, triclinic, CazMg4FeHSb5+0z mission in 1973, and the species and name were A, [Si4Bez018], a = 10'28 A, b = 10'69 A, c = 8'83 subsequently approved. I)( y = 106'1°, P = 96'3°, = 124.8°, PI with pseudo-mono- In the winter of 1975, I discovered twelve hand 9.68(1) A, bm clinic cell am = = 14'77(2) A, Cm= 5'I4(r) A, specimens of the new mineral in the Gustav Flink Pm = 101'5(2)°, c-centred, occurs as lustrous subadaman- collection of Langban minerals at Harvard tine, thick prismatic reddish-black crystals up to 3 mm in greatest dimension associated with romeite, adelite, University and Professor Clifford Frondel kindly swedenborgite, berzeliite, manganoan phlogopite, permitted the sacrifice of two specimens towards richterite in crystalline dolomite from Umgban, Sweden. determination ofBeO. The present communication Forms include b{OIO}, a{Ioo}, k{I30}, m{rro}, j{02I}, is a formal description of the new species. p{ I I I}, q{ 12I}, v{ 13I}, r{I I I}, s{I2I}, t{I3I}, and v{I4I} Occurrence and paragenesis. The only locality for (monoclinic setting). Streak pale-brown, hardness 6, welshite is the famous manganese and iron mines at specific gravity 3'77, fracture conchoidal, no cleavage, Langban, Viirmland, Sweden. The specimens I)( = 1'81(1), Y = 1'83(1), 2E(obs.) - 45°, no noticeable I originated from Dr. G. Flink who communicated pleochroism. these as unknowns Nos. 450 and 451 (Flink, 1927). Welshite is a new member of the aenigmatite-rhonite But few specimens have been preserved; in addition group and obtains from the substitution Sb5+ --->Ti4 + and Be2+ --->AIH in rhonite. to the Harvard specimens, the type (deposited in the collection at the U.S. National Museum of Natural History), one specimen presented to Mr. W. R. IN 1967, I announced eleven new minerals from Welsh, and two paratypes in the Swedish Natural Langban and Nordmark, Sweden of which two, History Museum (Stockholm), the only other speci- numbers 10 and 1I, were not yet named. Number mens to my knowledge are tiny fragments distri- IO proved, by a circuitous route, to be magnus- buted upon request to a few other museums. sonite and investigation on that material was Therefore, some discussion of associated minerals subsequently reported elsewhere (Moore, I97oa). is desirable. Number 1I, given the formula Caz(Mg, Fe)4 Welshite occurs as lustrous, subadamantine, SbSi40dOH)8 in Moore (1967), was far less thick prismatic reddish-black crystals up to 3 mm tractable. Further study on the material, includ- in greatest dimension. The crystals occur very ing a qualitative determination of Be, a partial locally, densely sprinkled in rather compact crystal- crystal structure analysis, and a suspected relation- line (1-2 mm grain size) dolomite, which fills ship with rh6nite, Caz(Mg, Fe)4FeHTi4+0z fractures in dense fine-grained hematite ore. Acces- [Si3AI3018J, completed the study. Unfortu- sory minerals in the dolomite include berzeliite, nately, neither quantitative Be nor a completed manganoan phlogopite, richterite, and occasional structure determination was obtained. A name, hausmannite grains. In close association with the welshite, was subsequently announced (Moore, welshite are orange romeite (val. weslienite) as 1970b) and the formula was presented as CazMg4 rounded octahedra, pale greenish-yellow waxy SbFeOz[Be3Si3018J, although neither descrip- grains of adelite, and, very rarely, swedenborgite. tion nor data were offered for the material. Dr. Welshite is yet another example of an antimony- Michael Fleischer (U.S. Geological Survey) in- bearing skarn product from Langban. It occurs in a formed me that the species had never been re- paragenesis similar to the other antimony-bearing viewed by the International Commission on New minerals romeite, CazSbz06F; swedenborgite, Minerals and New Mineral Names. After further NaSbBe407; katoptrite, Mn13SbzAI4SizOz8; search for more material proved fruitless, I sub- langbanite, Mn~+Mn~+SbSizOz4; mangano- mitted the name and the data at hand to the Com- stibite, Mn7SbAs012; and stenhuggarite, (Q Copyright the Mineralogical Society 130 P. B. MOORE CaFeH SbH As~+07, In addition, it is allied was discovered that the mineral is a member of the chemically to the beryllosilicate clinoamphibole aenigmatite group. Walenta (1969), in a detailed joesmithite, PbCazMg4Fe3 + (OH)z[Si6BezOn], study on the member rhonite, Caz(Mg, Fe)4 although the two minerals have not been found FeHTi4+0z[Si3AI30Is], pointed out that a pro- together. Moore (1970b) has interpreted these nounced pseudo-monoclinic cell for aenigma- curious minerals as products of thermal re- tite could be discerned, which is c-centred and crystallization oflocal concentrations of antimony- which is the orientation adopted for the present and arsenic-bearing complexes admixed in the iron study. Weak extra reflections require that the bm- and manganese oxide proto-ores. The presence of and Cm-axesbe doubled. Adopting the convention beryllium is unusual; it probably derived from a of Walenta (1969), the relationship of the pseudo- separate source in which case the peculiar combina- monoclinic cells for welshite and aenigmatite can tion of As, Sb, and Be is of 'accidental' occur- be readily discerned: rence, accounting for the extreme rarity of these Welshite Aenigmatite minerals outside this extremely local source. Physical properties. Welshite is deep reddish- am (A) 9'68(1) 9'888 (A) brown to reddish-black, brownish-orange in trans- bm 14'77(2) 14'814 Cm (A) S'I<j(I) mitted light. The colour varies somewhat probably S'z03 Pm 1010 30(ro') 102021' resulting from variations in the oxidation grade of the iron in the mineral. The crystals closely resemble clinopyroxenes in habit but differ in possessing a much higher luster. The streak is pale brown, hardness 6, specific gravity 3'77 (Berman DC, toluene as the dis- torsion balance, T = Z1'0 placed fluid). The fracture is conchoidal; no evidence of cleavage could be produced. The crystals are insoluble in dilute to strong HCl solu- tions and remain unaltered even after a period of one week. Optically, welshite shows low birefringence and A lack of cleavage did not admit orientation of the indicatrix. The isogyres are broad and the inter- ference figures sufficiently blurred to inhibit inter- A pretation of the sign. Biaxial, (X= 1'81(1), Y= 1'83(1), zE(obs) ~ 450. The grains are not dis- cernibly pleochroic. Crystallographic properties. Welshite is a mem- I I ber of the aenigmatite group and enjoys the same I I I I complex cell-pseudo cell relationships and per- I I I I I sistent poly synthetic twinning of that triclinic I : I I I I I I I phase. Crystals are usually stout prismatic parallel I I I I I I I I , I I I to the cm-axis although occasional individuals thick I I , ,I I I I I I I I I I I tabular parallel to b{01O} are also encountered. J k b - Y-~-,~ :a I m The facets are lustrous and remarkably free from I I I I I I etching, presenting excellent signals on the two- b/ " I , I , I : circle reflection goniometer. Forms observed in- , , " I I I I I I I I I I : I clude b{OIO}, a{lOo}, k{130}, m{IIo}, j{OZI}, I _1. _ , I I ) 1. I , ~, p{III}, q{IZI}, v{131}, r{III}, S{IZI}, t{I31}, and k , v{I4 I}. The indexing of the forms adopts the linear la, m I" ,I f elements of the pseudo-monoclinic cell (am,bm, Cm, f I f I I 13m)owing to obvious pseudo-monoclinic develop- , I ment of the crystals. The pseudo-monoclinic axial " I ratios are 0.6554: I: 0'3480, 13= 10I°30', adopted B from the X-ray study. All crystals examined were B polysynthetically twinned on {01O}. Two typical FIG. I. Two typical habits for welshite, Langban, Sweden, habits are shown in fig. I. showing the forms b{OIO}, a{roo}, k{130}, m{llo}, The X-ray study on welshite, initiated in 1966, p{III}, q{IZI}, and S{I21}. A, plan. B, clinographic presented problems that were not resolved until it projection. WELSHITE J3' The data for welshite were obtained from am-, bm-, Chemical composition, Owing to the meagre and cm-axis rotation photographs (Cu-Ket radia- quantity ofwelshite available, a complete chemical tion) and bm- and cm-axis precession photographs analysis was not possible, Emission spectrographic (Mo-Ket radiation) of the zero levels, analysis revealed major Be, Ca, Si, Mg, Mn, Sb, As, Machin and Siisse (1974), in a detailed crystal Fe, minor AI, and a trace of B, A crystal of the type structure analysis on serendibite, another member specimen was sacrificed for quantitative electron- of the aenigmatite group of structures, list the probe analysis, performed in 1966, but it was not triclinic reduced cells for welshite and six other until 1975 that sufficient material from two speci- members of that group, Their study is sufficiently mens in the Harvard collection was available for complete and detailed discussion here is unneces- BeO determination, The probe data were corrected sary, ]'hey applied the transformation matrix for absorption and efficiency-of-generation effects (002/gI/t!o) to the pseudo-monoclinic cell of and utilized the following standards: anorthite (Ca, welshite, obtaining a = IQ'28 A, b = IQ'69 A, c AI, Si); diopside (Ca, Mg, Si); knebelite (Fe, Mg, =8'83 A, et= 106'1°, f3=93'3°, and y= 124'8°, Mn); and arsenic and antimony metals, Twenty space group PI, for the true welshite cell, In sample points over three crystals afforded, after addition to the serendibite structure study by these correction: CaO 14'2(0'3), MnO 1'0(0'1), MgO scientists, Merlino (1970) and Cannillo, Mazzi, 15'3(0'3), Fe203 9'1(0'8), Alz03 2'1(0'2), SiOz Fang, Robinson, and Ohya (1971) have published 19'6(0'2), AszOs 3'6(0'4), SbzOs 24'8(2'8) wt %' The detailed accounts of the aenigmatite crystal determination of BeO = 4'0 % was obtained from structure, 4°'0 mg of crystals and I am indebted to Dr.
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  • Khmaralite, a New Beryllium-Bearing Mineral Related to Sapphirine: a Superstructure Resulting from Partial Ordering of Be, Al, and Si on Tetrahedral Sites

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    American Mineralogist, Volume 84, pages 1650–1660, 1999 Khmaralite, a new beryllium-bearing mineral related to sapphirine: A superstructure resulting from partial ordering of Be, Al, and Si on tetrahedral sites JACQUES BARBIER,1,* EDWARD S. GREW,2 PAULUS B. MOORE,3 AND SHU-CHUN SU4 1Department of Chemistry, McMaster University, Hamilton, Ontario, L8S 4M1 Canada 2Department of Geological Sciences, University of Maine 5790 Bryand Center Orono, Maine 04469, U.S.A. 3P.O. Box 703, Warwick, New York,10990, U.S.A. 4Hercules Research Center, 500 Hercules Road, Wilmington, Delaware 19808, U.S.A. ABSTRACT 3+ 2+ Khmaralite, Ca0.04Mg5.46Fe 0.12Fe 1.87Al14.26Be1.43B0.02Si4.80O40, is a new mineral closely related to sapphirine from Khmara Bay, Enderby Land, Antarctica. It occurs in a pegmatite metamorphosed at T ≥ 820 °C, P ≥ 10 kbar. The minerals surinamite, musgravite, and sillimanite associated with khmaralite at Casey Bay saturate it in BeO, and thus its BeO content could be close to the maximum possible. Optically, khmaralite is biaxial (–); at λ = 589 nm, α = 1.725(2), β = 1.740(2), γ = 1.741(2), 2Vmeas = 34.4 (1.8)°, v > r strong, and β b. The weak superstructure reported using electron diffraction has been confirmed by single-crystal X-ray diffraction. The superstructure corresponds to a doubling of the a axis in monoclinic sapphirine-2M (P21/c setting) with the following unit-cell parameters: a = 3 19.800(1), b = 14.371(1), c = 11.254(1) Å, β = 125.53(1)°, Z = 4, Dcalc = 3.61 g/cm .
  • The Crystal Structure of Aenigmatite E

    The Crystal Structure of Aenigmatite E

    THE AMERICAN MINERALOGIST, VOL. 56, MARCH-APRIL, 1971 THE CRYSTAL STRUCTURE OF AENIGMATITE E. CANNILLO AND F. MAZZI, Centro di studio del C.N.R. per la cristal- lografia struturale, Istituto di Mineralogia dell' Universita di Pavia, Italy. AND J. H. FANG, PAUL D. ROBINSON, AND Y. OHYA, Department of Geology, Southern Illinois University, Carbondale, Illinois, U.S.A. ABSTRACT Aenigmatite, Na2Fe.TiSi602Q, is triclinic PI, with a= 10.406(13), b = 10.813(14), c=8.926(6) A, <>= 104° 56'(9), ~=96°52'(11), 1'= 125°19'(6), and Z = 2. The structure was solved, independently and simultaneously, by Patterson syntheses and by the symbolic addition procedure. Three-dimensional refinement with 921 "observed" reflections (photo- graphic data) from a Naujakasik, Greenland, crystal gave RhkZ=0.075 and with 1501 "observed" reflections (counter data) from a Kola, Greenland crystal gave Rhkl=O.072. A distinct pseudo-monoclinic symmetry, based on a cell with parameters: 11m= 12.120, b1O=2X14.815, c1O=1O.406 A, <>10=90°4', ~1O=127°9', 1'10=89°44' (matrix of transforma- tion [011jI22/100j), Z = 8, emphasizes the similarity of its crystal structure with that of sapphirine [(Mg, Alh02(Si, Al)6018, a=11.266, b=14.401, c=9.929 A, ~=125 °46', Z=4, space group P2i!a]. The crystal structure consists of two sets of polyhedral layers parallel to the pseudo- monoclinic (100) plane which alternate along the x*-direction. The first layer is formed by Fe-octahedra, Ti-octahedra and distorted Na-square antiprisms and the second by [Si601s]" chains connected by Fe-octahedra.
  • Mineral Index

    Mineral Index

    Mineral Index Abhurite T.73, T.355 Anandite-Zlvl, T.116, T.455 Actinolite T.115, T.475 Anandite-20r T.116, T.45S Adamite T.73,T.405, T.60S Ancylite-(Ce) T.74,T.35S Adelite T.115, T.40S Andalusite (VoU, T.52,T.22S), T.27S, T.60S Aegirine T.73, T.30S Andesine (VoU, T.58, T.22S), T.41S Aenigmatite T.115, T.46S Andorite T.74, T.31S Aerugite (VoU, T.64, T.22S), T.34S Andradite T.74, T.36S Agrellite T.115, T.47S Andremeyerite T.116, T.41S Aikinite T.73,T.27S, T.60S Andrewsite T.116, T.465 Akatoreite T.73, T.54S, T.615 Angelellite T.74,T.59S Akermanite T.73, T.33S Ankerite T.74,T.305 Aktashite T.73, T.36S Annite T.146, T.44S Albite T.73,T.30S, T.60S Anorthite T.74,T.415 Aleksite T.73, T.35S Anorthoclase T.74,T.30S, T.60S Alforsite T.73, T.325 Anthoinite T.74, T.31S Allactite T.73, T.38S Anthophyllite T.74, T.47S, T.61S Allanite-(Ce) T.146, T.51S Antigorite T.74,T.375, 60S Allanite-(La) T.115, T.44S Antlerite T.74, T.32S, T.60S Allanite-(Y) T.146, T.51S Apatite T.75, T.32S, T.60S Alleghanyite T.73, T.36S Aphthitalite T.75,T.42S, T.60 Allophane T.115, T.59S Apuanite T.75,T.34S Alluaudite T.115, T.45S Archerite T.75,T.31S Almandine T.73, T.36S Arctite T.146, T.53S Alstonite T.73,T.315 Arcubisite T.75, T.31S Althausite T.73,T.40S Ardaite T.75,T.39S Alumino-barroisite T.166, T.57S Ardennite T.166, T.55S Alumino-ferra-hornblende T.166, T.57S Arfvedsonite T.146, T.55S, T.61S Alumino-katophorite T.166, T.57S Argentojarosite T.116, T.45S Alumino-magnesio-hornblende T.159,T.555 Argentotennantite T.75,T.47S Alumino-taramite T.166, T.57S Argyrodite (VoU,