ORES OF COPPER

R7

higher parts of the lode now destroyed or may be due to
Primary deposition. ]
The copper-field is about 80 miles long and includes, actording
 to Finlayson (Econ. Geal., v, 1910, p. 407), thirtythree
 chief ore-bodies. The South Lode of Rio Tinto and its
continuation, the San Dionisio Lode, are together more than
I} miles long. La Zarza Lode and its continuation Perrunal
are together also 1} miles long, and their full length is not yet
known. La Rosa and the Sotiel are 11 50 and 900 yards long
Tespectively, Most of the ore-bodies are between 250 and
000 yards long. The San Dionisio is
800 feet wide, and most of the larger
lodes are between 150 and 500 feet wide.
Their depth is small ‘in relation to
their thickness, According to Finlayson
the depth probably in no case exceeded
about 3000 feet, and seldom 1500 feet.
Some of the ore-bodies are thicker below,
 as the upper part of the lenticle is
%ill preserved.” The ore-bodies eceur in
different rocks, According to Finlayson’s
 list four of them are in porphyry;
two at the junction of slate and diabase;
 eleven at that of slate and
Porphyry, as at Rio Tinto and Calanas
and sixteen are wholly enclosed in sedi-Qentary
 rocks, such as the Tharsis,
Sotiel, and El Tinto (Fig, 20) which are
In slate,
Mr. Lyra similar mass of copper- oo
bearing pyrite occurs at the Mt. Lyell Mine in Western
Tasmania,” 50 miles inland, N. of Macquarie Harbour.
Alluvia] gold was found in the district in 1881 and at Mt.
Lyell in 1383 ; in 1891 was found the *“ Iron Blow,” a gossan
Which contained gold and silver, and covered a large orebody
 of Pyrite containing sufficient copper to pay for mining,
the gold and silver being recovered as bye-products.
The Mt. Lyell Mines? occur close to the contact of the

YJ. W. Gre « os " : vis
: gory, “The Mt, Lyell Mining Field with other Pyritic
Ore Bodies,» Austral. 7M.E., 1905, viii. . 198.