hillebrand.] NOTES ON CALAVERITE FROM CRIPPLE CREEK. 59 
of the species. Interesting is the slight variation in the ratio between 
gold and silver, and the very low percentage of silver in the mineral 
from the C. O. D. and Raven mines. Calaverite, the lowest silver 
carrier of the gold-silver tellurides, has not heretofore been known to 
carry less than 3 per cent of silver. 
The pyrognostic characteristics of the mineral from the Prince 
Albert mine were essentially those ascribed to calaverite. In the closed 
tube it fuses, giving a white coating near the assay, and a globular 
gray coating just above, which latter by strong heat can be in part 
driven higher up, leaving the glass covered with the same white fused 
coating as lower down. This latter is yellow while hot. On charcoal 
the mineral fuses with a green flame, giving a white coating and 
similar fumes, and leaving a yellow bead. The color is pale bronze- 
yellow, in powder greenish gray. The hardness is not less than and 
perhaps a little over 3. Specific gravity, as given above, 9. 
The identity of the telluride occurring at Cripple Creek, which in 
oxidizing gives free gold and oxidized tellurium compounds, 1 seems thus 
satisfactorily established, but unless there is another richer in silver, 
as believed by Pearce, the mode of occurrence of the silver in some of 
the ores is still in large part unaccounted for. It may be derived from 
a very rich argentiferous tetrahedrite of which Professor Penrose sub 
mitted a small specimen for identification. This carries over 11 per 
cent of silver, but is said to be excessively scarce and therefore hardly 
to be considered in this connection, unless indeed this should have 
been the original source of most of the silver and later have suffered 
oxidation to a great extent whereby the silver has become more evenly 
distributed throughout the ore. 
Professor Pen field has kindly contributed the following notes on the 
crystallography of the mineral: 
The crystals of calaverite which were examined were developed with prismatic 
hahit, hut the prismatic zone was striated to such an extent that it was impossible 
to identify a single face in the zone, and on the reflecting goniometer almost an 
unbroken band of signals was obtained in a revolution of 360°. Owing to oscilla- 
tory combinations the crystals were also much distorted, so that they did not present 
regular cross sections. 
The prisms were attached so that doubly terminated ones were not observed, 
while the faces at the free end were small and developed with so little symmetry 
that after a study of a number of crystals it was found impossible to determine with 
certainty the system of crystallization. 
The crystals do not exhibit the perfect cleavage ascribed to sylvanite and kren- 
nerite, but are similar to the former in some of their angles. When placed in 
position to show their relation to sylvanite they have their prismatic development 
parallel to the b axis. One crystal, which owing to its development was more care- 
fully measured than any of the others, was apparently a twin about 101, and showed 
^rom tests made by myself on a number of specimens collected by Professor Penrose the combina- 
tion seems to be chiefly if not altogether with iron, but whether as tellurite or tellurate could not bo 
ascertained. Knight (loc. cit., p. 69), however, has shown that the combination, in some cases at 
least, is a tellurite, approximating to the formula 2(Fe20 3 , 2Te0 2 )+H 2 0. 
