ORES OF COPPER 05

Hecla Shoot, is in conglomerate ; it is about 3 miles long,
and varies from 12 to 15 feet thick, and has been mined
to the depth of over 6000 feet. The ore is low grade, and
has paid to work toa value of ‘55 per cent. of copper, for the
vein stuffs are brittle and cheaply crushed by stamps, and
the metallic copper is separated by simple washing. The
copper was at one time considered to have been a primary
constituent of the ferro-magnesian minerals in the diabase;
but the igneous rocks only contain copper where it has been
Secondarily introduced. The rocks near the ore have been
traversed by hot alkaline plutonic water which probably
obtained the copper by the solution of detrital grains in
the sandstones. The channels form the shoots, some of
which enter the lavas; the reduction of the solution by oxidation
 of ferrous iron in the diabase or of some ferrous mineral
In the conglomerate led to the deposition of the native
Copper.