W. H. Hobbs — Goldsehmidtite, a New Mineral. 357 



Art. XXXIX. — Goldsckmidtite, a New Mineral ; by 

 William H. Hobbs. 



The analyses of Hillebrand and the crystallographical studies 

 of Penfield which were made in connection with the mono- 

 graph of Cross and Penrose* on the Cripple Creek Mining 

 District have established the fact that the chief telluride ore of 

 the district is the mineral calaverite, containing about three 

 per cent, or less, of silver. The presence of this mineral in 

 the ores had previously been determined by Knightf by 

 chemical analysis. Mr. R. Pearce^: of Denver had, however, 

 assayed an ore-bearing rock from the Moose Mine, and found 

 it to contain gold, silver, and tellurium in proportions corre- 

 sponding with sylvanite, so that he believed this mineral to be 

 present. From the complex nature of the material assayed 

 these results can hardly be regarded as conclusive, but to the 

 writer they would seem to indicate at least the probability of 

 the presence of a gold-silver telluride, richer in silver than 

 calaverite, particularly since the output of silver from some of 

 the mines is too large to be fully accounted for by the presence 

 of calaverite alone. Dr. Hillebrand says : 



" Notwithstanding that sylvanite has not been identified by 

 positive chemical or crystallographical tests, the evidence of 

 Mr. Pearce as to its presence in some portions of the district at 

 least is entitled to consideration " (1. c, p. 133). 



Source of the Material examined. 



The material which I have studied was kindly given me for 

 examination by Mr. Gustavus Sessinghaus, a graduate of the 

 Columbia School of Mines, and now a graduate student of the 

 University of Wisconsin. It was obtained from the Gold 

 Dollar Mine in Arequa Gulch, in the extreme southwestern 

 portion of the Cripple Creek Mining District. This mine 

 is located on the northwest quarter of Section 31. (Cf. 

 Plate VII, 1. c) It is near the flank of Grouse Mountain. 

 The material consists of a single small hand specimen, the 

 matrix of which is a breccia in which fragments of granite 

 are conspicuous. Comparison with the gneissose granite of 

 Grouse Mountain shows that the enclosures in the rock have 

 probably been derived from that source. The cementing mate- 

 rial of the breccia resembles the phonolite of the region, with 



* Geology and Mining Industries of the Cripple Creek District, Colorado ; by 

 Whitman Cross and R. A. P. Penrose, Jr. 16th Ann. Report, U. S. Geol. Survey, 

 1894-5, Pt. II, pp. 1-209. 



f Proc. Colo. Sci. Soc, Oct. 1, 1894. J Ibid., April 5, 1894. 



