CELESTITE AND CALCIOSTRONTIANITE FROM WISE COUNTY, VIRGINIA Rrcneno S. MrrcnBrr., Llnittersity oj Virginia

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1 THE AMERICAN MINERALOGIST, VOL 46, IANUARY_FEBRUARY' 1961 CELESTITE AND CALCIOSTRONTIANITE FROM WISE COUNTY, VIRGINIA Rrcneno S. MrrcnBrr., Llnittersity oj Virginia AND

2 190 R. S. MITCHELL AND R. F. PEARR about 2 inches. Most of the crystals are elongated parallel to their a axes, and the {011} faces predominate. They can be conveniently classified into two main habits Habit A (Figs. 14 and 24) is the most common, and exhibits the greatest number of crystal forms. fn addition to the prominent {011} faces, which are frosted due to slight etching, they have relatively large, bright {101} faces and small lt22l, {2t0(, t21tl, tt 100}, {00i}, and {010} faces. Lving between {1221 and {210} (also Izrrl) ir'u dulr flat Frc. 1 (above). rdealized drawings of the two habits exhibited by celestite crystals Frc. 2 (berow). ceres ti te..[ti.h:"t;.:ilit/irginia'

3 CELESTITE AND CALCIOSTRONTIANITE IN' etching was observed. The vectorial etching is an outstanding property of the type A cryst The area between fl2)\ and' {210}, which may correspond to {11lJ' is affected the most, ll22l is next, and then [011]' Contrasted with tfese are the bright {100},{101},{210}, I2tll, and [001f' Apparentlv the faces have different susceptibilities to natural acids (probably carbopic) which circulated in the rock. Solution channels, roughly parallel to [0fO.f' deeply penetrate some of the crystals. No good etch figures were observed. A fragment of blue fibrous celestite, resembling satin spar gypsum' AS found loose in the quarry. The piece is tabular, measuring about an ch across and I inch thick, and probably represents a cross-fiber veinl t he fiber axes being perpendicular to the tablet surface' A study of thin tions of this material showed that the fibers are all elongated parall lto c. Thin sections cut perpendicular to the fibers showed bundles ith nearly parallel orientation, but adjacent bundles may have quite I ent orientation of the a and b axes. The individual fibers measure :om 0.02 to 0.12 mm. across, and the bundles are from 1 to 2 mm' OSS. Quite perfect cleavage, [001], was observed across the fibers' and less p'erf"ciinclined cleavage, presumably prismatic, {210}' was obser din thin sections cut perpendicular to the fiber direction' Cleavable masses of blue and white celestite up to 1 X 4 X 5 inches also observed filling veins and vugs in the quarry' Thin sections o the dolomite show embedded microscopic euhedral celestite crystals' X-ray difiraction powder data for the celestite showed no signi tl departure from that of pure strontium sulfate as reported by n uni Fuyat (1953). However, a semiquantitative spectrographic ysis of a specimen did reveal 0.157a CaO and 0'002/6 BaO' DpscnrprroN of THE CercrosrnoNTrANrrE calciostrontianite occurs intimately associated with celestite i the quarry, especially with celestite which is frosted or deeply cor Cal.iostro.rtianite forms vitreous to dull globular masses which 1 from an internal radial structure (Fig' 3). The size of the globules ranges light very small to a half inch in diameter. They vary in color from a

4 192 R. S. MITCHELL AND R. F. PHARR grayish-white to light bufi. Bright pale-green to cream fluorescence is exhibited under long-wave ultraviolet light (3600 to 3650 A. U.). The majority of the globules are rough and are terminated by small acicular crystals. Because of their extremely small size (width from 0.02 to 0.0g mm. and length from 0.1 to a little over 0.3 mm.) a precise determination of the morphology was not obtained. However, goniometric measurements, combined with measurements made on the microscope stage, show that the crystal needles consist mainly of an orthorhombic bipyra- Frc. 3 (left). calciostrontianite globurar masses attached to porous doromite. Ftc. 4 (right). rdealized drawing of pseudohexagonar calciosirontianite crystar. mid, either {8S1}, or a form close to it, and a brachydome, possibly l0'15.1. These forms combine to give a steep pseudohexagonal fyramid (Fig. a). rn some cases the pyramidal needres were somewhat curved and at times showed horizontal striations like material from Tyrol, described by cathrein (1888). According to palache, Berman, and Frondel (r951) steep pyramidal forms are frequently found in highly calcian strontianite. The presence of considerable amounts of calcium in the strontium carbonate was first suspected from the r-ray diffraction data. euantitative spectrographic analyses of speciallyselected and cleaned material revealed l.o7o CaO for a tan colored specimen, and L0/6 CaO for a white specimen.* Traces of Ba, Mg, Al and cu, listed here in the * These quantitative anaryses were performed by the American spectrographic Laboratories, Inc., San Francisco, California,

5 C ELESTIT E AN D CA LCIOST RON T I AN I T E nearly an identical amount of cao. Although the name emmonite was introduced earliest, the writers prefer to use calciostrontianite. Tenr,o I. A ConapanrsoN ol X-Rav PowoBn Der'q' ron CalcrostnoNTtANrrE lnou Wrsn CouNrv, Vrncrxra wrrn PunP SrCOa CuKa radiation; camera diameter 11'46 cm' Calciostrontianite dorr" A SrCOr* dl Calciostrontianite d"u" A SrCO:* dl tl 02l r t r vvs VS m m S- S s 132 IIJ )L'.) rrr! 1?Ll t t.49 1 Aj t.44 t.4l m w I.81 r r I I.)l r x Taken from Swanson, Fuyat and Ugrinic (1954)' The r-ray data in Table I represent an average of measurements made on four films from four different specimens. The unit c,ell constants are oo : 5.070, bo : and co : A latt A); oo bo I co " :0.611:1: These data show a significant departure from pure SrCOs. The data of Swanson, Fuyat and Ugrinic (1954) for pure SrCOa are also given in Table I. Their values or1- ao--5'1o7, b6:8'414 and co :6.02g A. No significant departure of refractive indices from values reported in the literature for natural strontianite was found' Calciostrontianite globules occur attached to the large blue celestite crystals, especially in the vicinity of solution channels, or along seams

6 L94 R. S. MITCHELL AND R. F. PHARR where two crystals are joined. Masses of porous doromite also contain globules of calciostrontianite attached to the walls of cavities, as well as tiny gemmy celestite crystals up to fi inch, and gemmy calcite scalenohedrons. Most evidence suggests that the calciostrontianite is secondary after celestite, and was probably formed by the reaction of carbonic acid on the sulfate. A thin section across a spherulite, which was situated at the junction of two celestite crystals, showed a channel Ieading out from the celestite with the globule perched at the orifice. perhaps these relationships suggest a mechanism whereby the globule of radial needres was formed. Assoctatpt MrNrrter,s ornpn occunnbwcbs ol cb*sure AND carcrosrnontranrre rn Vrncrxra Lozenge-shaped celestite crystals, up to j inch across occur in vugs in a quarry in Tonoloway limestone, of the Cayuga group, at Hayfield, Frederick County. Near Fulks Run, Rockingham County, small vugs and cavities in Tonoloway limestone contain celestite crystals. The discovery of these three occurrences of celestite in rocks of the cayuga group in widely separated sections of Virginia strongly suggests that strontium minerals may be found at other places in the state in rocks of this age. Dietrich (1960) has recently reported calciostrontianite, with small Athens formation (Middle ordovician) obtained near rrarrisonburg, Rockingham County. AcTNowTBoGMENTS The writers wish to express their gratitude to Mr. G. H. Belton for his cooperation in allowing them to examine and collect from his quarryl and also for making all the specimens he and his son collected for several

7 CELESTITE AN D CALCIOSTRONTIAN IT E 195 years available for study. Special thanks are due Dr. Bruce Hobbs, of the Virginia Division of Mineral Resources, for taking the photographs of celestite and calciostrontianite which are reproduced in this paper. R-nlrnBNcns Ce.ttnorx, A. (1888) Ueber Calciostrontianit (Emmonit) von Brixlegg: Z. Krist.,14, Drntnrcn, R. V. (1960), Calciostrontianite from Pulaski and Rockingham Counties, Virginia: Am. M iner al., 45, lll Euv, J. B. (1923), The geology and mineral resources of Wise County and the coal-bearing portion of Scott County, Virginia: Vi.rgini.a Geol,. Suroey, 8u1,1,.,24, Gnawn, O. R. (1956), Starkeyite, a correction: Am. Mineral.,4l,662. Pelncrn, C., Brnuew, H. ano Fnoxonr,, C. (1951), Dona's System oj Mineralogy (7th): New York, John Wiley, 2, Pnenn, R. F. eno Mrrcrsr,r, R. S. (1959), Celestite and strontianite from Wise County, Virginia: V,irginia J. Sci,., lo, 295. SwaNsoN, H. E. nxt Fuvar, R. K. (1953), Natl. Bur. Standarils (U. S.) Cire. 539,2, AND lfcnrnrc, G. M. (1954), Natl,. Bur. Standards (U. S.) Ci,rc. 539, 3, Tuousox, T. (1836) Description and analysis of emmonite, a new species of carbonated strontium from America: Record.s oj General Sci.enee, 3, Manuscript recehed, April 12, 1960.