bansome.] , ORE MINERALS. 79 
the principal constituent of ore bodies of some size and continuity, 
but in others, especially in those lodes carrying much galena, the 
tetrahedrite often occurs as bunches in the other ore. A little lead 
may sometimes replace part of the copper, as was found to be the 
case with a tetrahedrite carrying both arsenic and antimony, from 
the Black Diamond claim, on California Mountain. Tetrahedrite was 
present also in the ores of the Yankee Girl, Silver Bell, and other 
Red Mountain mines. 
Enargite.— Sulpharsenate of copper (3Cu 2 S.As 2 S 5 ). Contains 48.3 
percent of copper. Orthorhombic. One perfect cleavage. Grayish 
black to iron black. Hardness, 3. Brittle. Specific gravity, 4.4. 
Enargite is of somewhai frequent occurrence in the ores of the Red 
Mountain range. It was found abundantly in the Zuni and Congress 
mines, and formed the principal ore of the National Belle. Hand- 
sonic clusters of prismatic crystals incrusted with malachite and 
quartz were seen from the now inaccessible workings of this mine. 
According to Mr. Emmons, enargite occurred in the Yankee Girl. 
The enargite <>!' th<> Zuni mine is said to have carried over 200 
ounces of silver per ton. In the National Belle it was probably of 
much lower grade. 
Chalcocite. — Cuprous sulphide (Cu 2 S), corresponding to 79.8 per 
ceni of copper. Orthorhombic, commonly massive. Blackish lead- 
gray. Hardness, 2.5-3. Specific gravity, 5.5-5.8. 
Stromeyerite. — Sulphide of silver and copper ((AgCu 2 )S). Form 
and physical properties like chalcocite, except slightly higher specific 
gravity — 6. L— 6.3. 
These two closely related species do not always admit of sharp dis- 
tinction. Stromeyerite may be regarded as chalcocite in which about 
half of the copper is replaced by silver. Chalcocite is itself a valu- 
able ore mineral on account of its high percentage of copper, but 
stromeyerite, which may contain over 50 percent of silver, is particu- 
larly valuable. The two minerals are probably connected by inter- 
mediate varieties. 
Chalcocite, more or less argentiferous, was noted on the dump of the 
Frank Hough mine, and bornite in the Silver Link and John J. 
Crooke. Stromeyerite is reported to have been formerly an abundant 
ore in the Yankee Girl and Guston mines, where it occurred above a 
depth of 600 feet, between galena above and bornite below. One lot 
of <> tons of this rich ore from the Yankee Girl contained over 5,300 
ounces of silver per ton, 1 while one small lot from the sixth level of 
the Guston is stated to have contained 15,000 ounces of silver per ton, 
which corresponds roughly to the percentage of silver in pure stro- 
meyerite. None of this ore could be seen in 1809 or 1900. 
Some of the richest ore in the New York City lode, in the Silver 
Lake mine, contains small quantities of a black amorphous substance, 
1 Schwarz: Trans. Am. Inst. Min. Eng., Vol. XVIII, 1889-90, p. 145. 
