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Volume 47, pages 778-779, 1962 PARAMELACONITE AND ASSOCIATED MINERALS FROM THE ALGOMAH MINE, ONTONAGON COUNTY,MICHIGAN SIDNEY A. WILLIAMS, Department of Geology, Michigan College of Mining andTechnology, Houghton, Michigan. Since the first description of paramelaconite from the Copper Queen mine,Bisbee, Arizona, by Koenig in 1891, only two specimens have been known to exist.During the present study a third specimen from the type locality, donated byKoenig to the A. E. Seaman Museum at the Michigan College of Mining andTechnology, was found and used for purposes of comparison. The specimen is asmall, superb group of crystals associated with connellite and malachite. Several other specimens were found in the museum with the locality given as theAlgomah mine, Ontonagon County, Michigan. Examination of these specimensrevealed that all contain paramelaconite crystals, some reaching a length ofeight mm. The crystals are rough and pitted and of pseudocubical habit, althougha few individuals are pseudooctahedral. A few cavernous crystals were foundwhich contained small, highly perfect paramelaconite crystals in parallelorientation with the outer individual. Four of these crystals were examined onthe goniometer and the following forms noted: {001}, {010}, {110}, {013}, {011},{113} and {112}. All of these forms but {001}, {010} and {011} are new for thespecies. Two crystals exhibited {013} and {113} together and {110} and I {112}were found once, on each of the other two crystals respectively. The appearanceof all of these four crystals resembles the habit illustrated by Frondel (1941).The specific gravity of this material is 6.11 (average of four determinations onthe microbalance). The crystals occur in thin seams which are coated with poorly crystallizedmalachite and scattered small dioptase prisms. The matrix of the specimenscontains small blebs of cuprite which are ringed by tenorite and then chrysocolla.Blades of atacamite may be found embedded ill the chrysocolla. Veinlets ofgranular paramelaconite transect all of the minerals in these blebs. Dioptase isearlier than the paramelaconite be malachite is later; crystals of malachitecommonly line skeletal paramelaconite crystals. Professor K. Spiroff of the Department of Geology loaned the writer severalspecimens from the departmental collection which were obtained at the Algomah mine. Several of these specimens were identical to those justdescribed. A few, however, consist of massive paramelaconite which is coarselygranular and shows well developed basal parting. Close examination revealed thatthis material is pseudomorphous after quartz, and large, perfectly developedcrystals show the rhombohedra z and r, the prism, and one or more trigonaltrapezohedra. Veinlets of a fibrous blue mineral cutting the paramelaconite in these specimenswere examined and proved to be planchéite as defined by Billiet (1942). Theoptical properties of the planchéite are as follows: α=1.697; β=1.720, andγ=1.744. The optic sign is + with 2V approaching 90°. The pleochroism isfairly strong in blue; Z and Y are blue and X is sensibly colorless withZ>Y>X. The fibers show positive elongation and parallel extinction. Thin sections of this material show the sequencedioptase-paramelaconite-planchéite-malachite-chrysocolla. Perfect pseudomorphsof planchéite after dioptase are relatively common. On a recent collecting trip to the Algomah mine a few massive pieces ofparamelaconite were found, two of which contain small pockets of crystals. TheAlgomah mine is now closed and filled with water; it seems unlikely that it willever be reopened. The writer is grateful to Professor K. Spiroff of the Department of Geology,Michigan College of Mining and Technology, and to Professor John W. Anthony,Department of Geology, University of Arizona, for reading the manuscript andoffering helpful suggestions, REFERENCES BILLIET, V. (1942), Onderzoek het verband tusschen chrysocolla, katangiet,plancheiet, bisbeeiet, shattuckite en dioptaas. Verk. k. Vlaamsehe Acad.Wetensch Lett. Belgie. 4, l.
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