_Converter Bars._—The product from the Bessemer operation on copper
mattes. Most converter metal is subsequently electrolytically refined,
but several varieties of Australian and American copper are put on
the market direct in this form. Being produced from fairly pure ores,
which carry but little silver and gold, the converter metal may be
sufficiently pure to render electrolytic refining unnecessary, and too
low in gold and silver values to make such an operation profitable.
_Cathode Copper_ is the product from the electrolytic refinery, and is
usually remelted, brought up to pitch, and cast into ingots previous to
use.
_Black Copper_ is produced by the smelting of oxide ores, and is
subsequently refined.
_Cement Copper_ is produced by wet processes, usually by precipitation
from copper-bearing solutions by means of iron, the product being
a rather impure reddish-brown spongy mass. Many varieties contain
arsenic. It requires melting and subsequent refining to adapt it for
service.
_Blister Copper_ was the name given to the crude metal from the older
type of furnace operations. Such copper contained large quantities
of gas, particularly SO_{2}, which, tending to escape at the moment
of solidification in the mould, gave a blistered appearance to the
surface. It contained 96 to 98 per cent. of metallic copper, and was
subsequently refined. The term is generally applied still to all crude
copper exhibiting similar features.
_Chili Bar_ is an impure copper imported from Chili for refining. The
composition varies, the metal usually containing 96 to 98 per cent. of
copper, with indefinite quantities, sometimes small, of undesirable
impurities.
Appended is a series of representative analyses of various copper
products, compiled from different sources. The composition of such
material as tough pitch copper and the various cruder varieties is,
however, subject to very great variation.
=The Sources of Copper.=—Copper ores usually consist of various
minerals of copper mixed with those of many other metals, and
accompanied by very varied gangue, according to the locality in which
they are found.