ORES OF COPPER 8s
ores; they are typical fissure lodes of quartz with Sry
sulphides and pyrite, but have replaced some of the wa
rock. The Cornish copper mines have an extensive literatur €
(ef. J. H. Collins, W. of England Mining Region, 1912,
- XV-XX),
reas Soumm AUSTRALIA AND SoutH Arrica—The
Wallaroo Mines, near Moonta in South Australia, are quartz-
“halcopyrite loges in orthoclase-porphyry. The lodes are
bre-Palzozoic, as they do not pass up into the overlying
Cambrian. The ore forms deep pipe-like shoots, which con.
tain from 3 to 4 per cent. of copper and have been worked
to the depth of 2000 feet, } .
The Namaqualand copper ores of South Africa occur 1n
shallower pipes which have a regular quincuncial arrange-
Tent at the intersections of a network of fractures. Accord-
vos to Kuntz (Tr. G. Soc. 5. afr, vii 1904, p. 70) the pipes
occur where parallel joints cross lode-filled fractures; but
according to J. I. Ronaldson (ibid., viii, 1906, p. 161), the
Material in the fractures looks like dykes though it may be
altered pnejgs, The ores were obviously due to deposition
5Y solutions Passing along intersecting fissures.
Disseminations AND REPLACEMENTS — Fissure lodes are
often enlarged by the replacement of the walls. In some cases
the ore thyg deposited so greatly exceeds that in the fissures
that the result is 5 replacement lode,
The simplest replacement ores consist of scattered grains
Or small patches of copper sulphides, as in the olivine-gabbro
of Monte Catini in Tuscany, Cuba, and Turkey. The rock
beside the Monte Catini gabbre has been altered to a fractured
serpentine which contains veins of copper ore.
. The second type is commercially more important, and
Includes masses of copper ore in limestones, as at Chillagoe
in Queensland ; the solutions having been neutralized by
the limestone, the Copper minerals were deposited by its
replacement, Analogous ores occur in tuffs at Boundary
Creek, British Columbia,
A third 8roup of replacement ores are formed as contact
products, chiefly beside intrusions of porphyry and diabase
into limestone, They occur on a small scale at Campiglia
Marittima ip Tuscany, at the contact of diabase with Liassic
limestone, ang near Oslo in Norway. The most important
