ORES OF FIVE MINOR METALS 127
fragments cemented by veins of stibnite; lenticular bodies
of ore show the tendency towards nodular masses. Tegengren
reports that the stibnite is a replacement of fractured rock.
An essentially similar process has formed the ores at the
Chiang-Ch’i-lung and Pan-Ch'i Mines, which are both in the
basin of the Tze River, a southern tributary of the Yangtze-
kiang in Hunan. At both localities the rocks, in addition
to having been folded and fractured, have been invaded by
Intrusive rocks which appear to have no essential connection
with the ores. The antimony at the Chiang-Ch’i-lung Mines
Is replaced at a depth of from 300 to 400 feet by pyrites.
The nodular masses of antimony ore are replacements by
solutions moving vertically, as they are independent of the
rocks in which they occur. The concentration is due to
the solubility of stibnite in water at 180° F.; hence small
particles are readily dissolved, and the sulphide remains in
solution until near the surface, where it is deposited in a
concentrated form by the replacement of various rocks.
The amount of antimony in the lodes generally falls rapidly
In depth, and it is replaced by various minerals such as ores
of zinc in Arkansas, pyrites in some Chinese deposits, and
scheelite (CaWO,) in Sardinia.
ARSENIC
Arsenic (As; at. wt, 75; sp. gr., 57; vaporization,
800° F.; volatilization begins at 212°) is very widely dis-
tributed as it is a constituent of 130 or about 12 per cent.
of the known mineral species. Its chief ores are mispickel
Or arsenical pyrites (FeAsS), which contains 46 per cent.
of arsenic; realgar (AsS), and orpiment (As,Sg). Its main
uses are to decolor glass and as a pigment, a drug, an insecti-
cide and weed-killer, and preservative in arsenical soap.
During the War it was used to harden shot, owing to the
scarcity of antimony.
It is usually carried into its ores in solution, but it enters
tock cavities as vapour and is deposited on the roof as
small crystals of realgar. It is often associated with copper,
and was produced from the upper part of the Cornish copper
zone, and was found, as at Dolcoath, at a depth of 500 to goo
feet: it is deposited after tin. as it occurs in the middle crust of
