114 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. |bull. 213. 
rich black copper-sulphide ore associated with cupriferous pyrite from 
the large mines have been found by Dr. H. N. Stokes, chemist of the 
Survey, to consist mainly of tetrahedrite (copper-antimony sulphide 
with silver, zinc, and arsenic associated; gray copper). This is not 
like normal tetrahedrite of some camps, and is believed to be inti- 
mately associated with chalcocite (black sulphide of copper) and pos- 
sibly some melaconite (black oxide of copper). 
In this camp tetrahedrite occurs occasionally in crystalline form, 
but more commonly, and far more prevalently than has hitherto been 
recognized, under two facies of the massive form. In the copper ores 
in limestone it occurs in large masses as a dull-black powder and a 
crushed gray metallic substance associated with cupriferous pyrite. 
In the lead-silver fissure ores it occurs in regular bands and patches, 
is fine grained, compact, homogeneous, with metallic luster, steel-lead 
gray color, pale-bronze line, and gives a dark-red streak. This 
species, freibergite, contains silver, and is commonly mistaken for 
ruby silver. Exceptionally fine crystals of enargite (sulphide of 
copper and arsenic) were obtained from a single occurrence. An 
excellent specimen of pisanite (hydrous sulphate of copper and iron), 
an alteration product of copper ores, was supplied by Mr. A. F. 
Holden, who suggested that it might be this mineral. It is believed 
that this is I he first occurrence of the mineral reported in this 
country. Other copper-bearing minerals which occur in Bingham are 
bornite, covellite, cuprite, malachite, azurite, chalcanthite, native 
copper, and possibly cubanite, binnite, bournonite, and tennantite. 
(ialena (lead sulphide), which forms the bulk of all the present 
shipments of lead and silver, occurs in tabular bodies in or adjacent 
to fractures which intersect limestone^ shale, porphyry, or quartzite, 
or in two or more of these. Although it is sometimes scattered in 
small amounts through the limestone, it occurs more commonly in 
irregular bands roughly intercrustified witli similar bands of pyrite 
and chalcopyrite, calcite or quartz, and blende. Lead occurs here 
also in cerussite (carbonate of lead), anglesite (sulphate of lead), 
yellow oxide, and dufrenoysite. 
Silver values probably lie chiefly in galena. It is a matter of com- 
mon report among mining men that the granular variety of galena 
carries higher silver values than the cleavable variety. An assay by 
Dr. E. T. Allen, chemist of this Survey, of a composite sample of 
cleavable galena from four of the best-known silver-lead mines in 
Bingham, shows 18.9 ounces silver present, and of a sample of granu- 1 
lar galena only 10 ounces. Native silver has been reported, but was 
not found during the present survey, although it was suspected to 
occur. Ruby silver has not been found. Crystalline specimens 
reported to be ruby silver have been proved, on study of the crystal 
forms, to belong to a different crystal system, and on chemical deter- 1 
minations by Dr. Ilillebrand and Dr. Allen, of this Survey, have been 
