310 F. A. Genth—Contributions to Mineralogy. 
silver, in which a large portion of silver is replaced by gold, 
the so-called petzite, appears to be the most common. 
The specimens which I have examined, both from the Stan- 
islaus mine and from the Golden Rule mine, were without crys- 
talline structure, showed a distinct conchoidal fracture, metallic 
luster and a color between dark steel gray and iron black, some- 
times tarnished with pavonine colors. Brittle, soft, hardness 
about 25, sp. gr. according to Kiistel 9—9-4. Streak, iron black. 
B.B. with soda gives a bluish green flame and yields a silver 
globule of a yellowish white color. Ifa fragment is place 
e material for the analyses, highly magnified, was found 
to be free from admixtures with the exception of a minute 
quantity of quartz, which was deducted as follows: from analy- 
I ‘60 p.c., from IT, 0-99 p. c., from IV, 0°48 p.c., and from 
V, 0°59 p.e. 
Stanislaus Mine. Golden Rule Mine. 
I. II. Til. (Kiistel). IV. Vv. 
Gold, 25°55 25°70 24°80 25°60 24:97 
Silver, 41°93 . 42°36 40°60 41°86 40°87 
Tellurium, 32°52"  31°94* 35-40? 32°68 34°16" 
100700 100°00 ~=100°80 100°14 100°00 
These analyses correspond closely with the composition, ex- 
pressed by the formula: AuTe+3AgTe, which requires: 
Au, 197 25°35 
3Ag, 824 41°70 
4Te, 256 32°95 
777 
_ This variety of auriferous tellurid of silver is closely allied 
to that from Nagy-Ag, analyzed by Petz, but it contains a con- 
siderably higher ol i 
e analysis of Petz 
ling this difference in composition, they should 
: species, gold being capable of re- 
