MINERALOGICAL NOTES. 
By W. F. HlLLEBRAND. 
1. Calaverite from Cripple Creek, Colorado. 
The occurrence of tellurium in the ores of the mining district of 
Cripple Creek, Colorado, has been known from an early day in the as 
yet brief industrial hi story of that region. That it was, in part at 
least, associated with gold was likewise known from the observance 
of a crystallized gold tellurium mineral. Although the ores of the 
district are chiefly gold carriers, they contain also a little silver, and 
since recognized silver minerals had not been observed, or at most only 
in minute amount, it seemed probable that the silver was associated 
with the gold in the tellurium compound. Indeed, Mr. E. Pearce, of 
Denver, came to the conclusion, from analyses of oxidized and unoxi- 
dized ores, 1 that this mineral was sylvanite, and he says: a Sylvanite 
itself appeared in little silver white specks disseminated through a 
mass of greenish rhyolite." Notwithstanding that F. C. Knight 2 has 
identified calaverite by analysis and that sylvanite has not been identi- 
fied by positive chemical and crystallographical tests, the evidence of 
Mr. Pearce as to its presence, in some portions of the district at least, 
is entitled to consideration. 
The telluride examined by me was collected by E. A. F. Penrose, jr., 
who procured his material from three different mines in order to ascer- 
tain whether it was of constant or varying composition, or, in fact, 
whether there might not be more than one specific compound. That 
the composition does vary within narrow limits the analyses show ; but 
there is no reason apparent for assuming the existence of more than 
one species in the ores of these particular mines. 
The material from the Prince Albert mine, the first received, was 
with little trouble brought into an almost ideal condition of purity. It 
was in part apparently fairly well crystallized, but the measurements 
made by Prof. S. L. Pen field, of New Haven, are unfortunately not 
decisive as to the system of crystallization, as shown by his notes at 
the close of this paper. The specific gravity of this material was 8.91 
at 24° C, which becomes 9 when corrected for a small admixture of 
silico-ferruginous gangue of assumed specific gravity 2.70 (probably 
1 Proc. Colorado Sci. Soc, Vol. V, 1894, pp. 5, 11. 2 Ibid., Vol.V, 1894, p. 70. 
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