26 
ECONOMIC GEOLOGY 
ores of this type are in the Rocky Mountains, and have given 
rise to great secondary enrichments. 
Pvyritic Masses—Spain anp Mr. Lyeri—Historically the 
most famous of copper deposits are great lenticular masses 
of iron pyrites containing a small percentage of copper in 
South-western Spain—the Tarshish whence Solomon obtained 
copper for his temple. Mining was begun there in pre- 
historic times with stone tools, and continued by the Phoeni- 
cians, and the Romans who mined there on a colossal scale. 
After a prolonged interval, the field was re-opened about 
1850. The ore is low in grade; most of the primary ore 
contains between -2 and ‘8 per cent. of copper, though some 
ore in the upper parts, probably owing to enrichment, con- 
tained 3 per cent. of copper. Much of the ore is used for the 
manufacture of sulphuric acid, the copper being recovered 
as a bye-product. The chief mines are near Rio Tinto and 
Tharsis, N. of the port of Huelva. The mining area is bounded 
to the N. by pre-Cambrian gneisses, schists, and crystalline 
limestones, in the Sierra de Aracena, and some Cambrian 
rocks. The mining fields are in a broad band of slates, 
shales, and quartzites of Silurian, Devonian, and Lower 
Carboniferous age. These rocks have been invaded by 
granites, quartz-porphyries, trachytes, and diabases, and 
some of them have been crushed and sheared by the Altaid 
mountain movements, which have given the sedimentary 
rocks a general strike of E. and W. All the igneous rocks 
have been regarded as intrusive (as by Vogt, Finlayson, and 
Edge); but the diabase, as near Zalamea, includes tuffs, 
agglomerates, and pillow-lavas. 
The ore deposits consist of many enormous lenticular or 
boat-shaped masses of iron pyrites. The ore is sharply 
separated from the country rock or the two pass into one 
another; the ore is usually massive, but is in places banded. 
The transition in places from clean slate or porphyry through 
rock mixed with pyrites into pure pyrites, and the microscopic 
evidence support the view that the ore was formed by the 
gradual replacement of the country. The ore-bodies near 
the margin in places contain inclusions of rock, which are 
exceptional in the middle, where the replacement has been 
complete. The upper part of the ore-body is sometimes 
richest in copper, which may have been concentrated from