82 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull. 182. 
Guitermanite. — Sulpharsenite of lead (3PbS.As 2 S 3 ). Massive, 
compact. Bluish gray. Hardness, 3. Specific gravity, 5.9. 
This mineral, with zunyite, was first described and named by Dr. 
Hillebrand 1 , and occurs, as far as known, only in the Zimi and adja- 
cent claims. It always incloses the minute, sparkling tetrahedrons 
of zunyite, and is intimately associated with pyrite, enargite, kaolin, 
and barite. It alters superficial!} 7 to anglesite. As it contains about 
60 per cent of lead, and probably some silver, it is a valuable ore. 
Stibnite. — Antimony sulphide (Sb 2 S 3 ). Orthorhombic. Usualry in 
clusters of radiating prisms. Perfect cleavage in one direction. 
Lead gray. Hardness, 2. Specific gravity, 4.5. 
A single specimen of this mineral was seen, which was stated on 
reliable authority to have come from the North Star mine on Sul- 
tan Mountain. It is readily distinguished by its lustrous cleavage 
surfaces and softness, being easily scratched with the finger nail. 
Polybasite. — Sulphantimonite of silver (9AgS.Sb 2 S 3 ), with part of 
silver replaced by copper and jDart of antimony b} 7 arsenic. Ortho- 
rhombic. In characteristic, short, six-sided tabular prisms, with tri- 
angular striatums and beveled edges. Iron-black. Hardness, 2 to 3. 
Specific gravity, (5.1. 
This rich silver ore is known to have occurred in the upper work- 
ings of the Yankee Girl, and probably in other mines of the Red 
Mountain district. Well-crystallized specimens from this region are 
preserved in the museum of the Bureau of Mines, Denver, and in 
various private cabinets. 
Proustite (ruby silver). — Sulpharsenite of silver (3Ag 2 S.As^.S), cor- 
responding to 65.-4 per cent of silver. Rhombohedral, hemimorphic. 
Luster, adamantine. Transparent to translucent. Color, scarlet- 
vermilion, but somewhat masked by brilliant luster. Hardness, 2.25. 
Brittle. Specific gravity, 5.5 to 5.G. 
Few of the ores now mined show this mineral, although it was seem 
in the Ben Butler mine, associated with galena and perhaps argen- 
tite. It is also known in the Ridgeway mine and has been reported on 
good authority from the Red Cloud, Polar Star, Mammoth, Annie 
Wood, Palmetto, and AVheel of Fortune mines. It is known to have 
occurred in the Yankee Girl, and a specimen was seen which was said 
to have come from the Genesee- Vanderbilt mine. It characterizes 
the upper portions of argentiferous ore bodies and is not known at 
depths over a few hundred feet. 
Bismuthinite. — Sulphide of bismuth (Bi 2 S 3 ). Orthorhombic. One 
perfect cleavage. Lead-gray. Hardness, 2. Somewhat sectile. Spe- 
cific gravity, 6.5. 
This sulphide of bismuth occurs in slender prismatic crystals, witl 
specular ite in quartz at the Neigold claim on the south slope of Gal em 
Mountain. 
1 On zunyite and guitermanite, two new minerals from Colorado: Proc. Colo. Sci. Soc, Vol.! 
1884, pp. 129-131. Also Bull. U. S. Geol. Survey No. 20, 1885. 
