Penfield and Ford — Calaverite. 225 



Aet. XXYL — On Calaverite ; by S. L. Penfield and W. E. 



Ford. 



Introduction. — In 1868 the late Professor F. A. Genth* 

 assigned the name Calaverite to a massive telluride of gold, 

 from the Stanislaus Mine, Calaveras County, California. It 

 was shown by his analyses that it contained but little silver 

 (3*0 to 3*5 per cent), thus differing from sylvanite from Tran- 

 sylvania which contains from 11 to 13 per cent. It corre- 

 sponds, however, like sylvanite, to the general formula 

 [Au,Ag]Te 2 . He described it as having a bronze-yellow color 

 and an uneven to subconchoidal fracture. As far as the dif- 

 ference in chemical composition between sylvanite and cala- 

 verite are concerned, it might be questioned whether the latter 

 has a right to be regarded as a distinct species, for in their 

 combinations with tellurium, gold and silver are isomorphous. 

 Calaverite, however, has been supposed to have a crystalline 

 structure different from that of sylvanite, for it has no distinct 

 cleavage, and this property is one of the best means of dis- 

 tinguishing the mineral from sylvanite, which has a perfect 

 cleavage in one direction, parallel to the clino-pinacoid. Kren- 

 nerite, also, the orthorhombic species of the same general 

 formula, [Au,Ag]Te 2 , has a perfect cleavage, parallel to the 

 base. 



Calaverite was later described by Genthf from Boulder, 

 Colorado, two analyses being given, one showing 2'24 and the 

 other 3-03 per cent of silver. In 1895 W. F. Hillebrand^ 

 described calaverite from Cripple Creek, Colorado, giving 

 three analyses of materials from different mines, containing 

 respectively 3*23, 1*77 and 0*90 per cent of silver. The mate- 

 rial for the first analysis given by him was from the Prince 

 Albert Mine. It was well crystallized, and was sent to one of 

 the writers of this paper (Penfield) for examination. The 

 crystals, however, proved to be unusually perplexing, and 

 although considerable time was spent in studying them the 

 investigation did not lead to decisive results. In a brief note 

 accompanying Dr. Hillebrand's article, it was stated that the 

 crystals had certain angles which were nearly like those of 

 sylvanite, and that with the material then at hand it did 

 not seem possible to establish the system of crystallization with 

 certainty. It was suggested, because of the lack of symmetry 

 in the distribution of the faces, that the crystals probably 

 belonged to the triclinic system. 



* This Journal (2). xlv, p. 314. 



t Am. Phil. Soc, xiv. p. 229, 1874 and xvii, p. 117, 1877. 



X This Journal (3), 1, p. 128. 



