384 The American Geologist. •'"°«' ^^^^ 
and southerly and there is a tendency toward an easterly 
dip which is quite variable. At times, however, the stri4<:e 
is curved and the veins are almost crescent-shaped. At 
other times, the deposits appear to be limited in depth and 
confined to pockets of very rich ore on the surface of the 
ground. This mode of occurrence together with the chal- 
cedonic silica and the very fine condition of the gold even 
in the bonanza ore, added to the rotted appearance of the 
rocks all indicate deposition by hot spring action, and make 
it certain that the rich ore bodies are irregular in shape and 
extent and that they may often be expected to occur in 
chimneys and shoots of roughly cylindrical form, rather 
than in well defined veins continuously and uniformly min- 
eralized. At the same time, there are abundant evidences 
of movement, and of mineralization along fissures and dikes 
in some of the principal mines near Columbia mountain. 
Thus in the Florence there are stopes some 200 feet deep, 
200 feet long, and from six to fifteen feet between walls 
which are marked by clay selvage, planes of movement, 
drag pebbles and all the indications of strong fissures. 
Similar indications of extensive shattering are seen in the 
January and- Jumbo; and may be developed in depth on 
other properties where not visible in the surface workings. 
The oxidized ore at Goldfield is valuable solely for 
gold. Silver is almost wholl}^ absent, as are lead and cop- 
per. Pyrite particles are visible in the harder portions of the 
quartz. Below the water level the ore contains gray cop- 
per, bismuthinite (bismuth sulphide) and some tellurides. 
The gray copper is rich in gold. One assay of a sample 
from the Florence mine at the depth of 250 feet gave sev- 
enty ounces of gold and seven ounces of silver. The ore 
from this level of the Florence all carries copper and will 
average possibly two per cent, while the first class ore con- 
tains about seven per cent. The bismuthinite is generally 
associated with rich ore in which the native gold is seen 
sprinkled all through the rock in intimate relation with the 
brilliant needles of the bismuth mineral. Free gold was 
not noticed in the gray copper. 
There is abundant evidence of secondary enrichment 
in the .shape of films, rich deposits in cracks and crevices 
