_Requiebro_ are
middlings of medium richness, _China_ are smalls, and _Vaciscos_ the
finest ore. Besides native mercury, which the ores of Almaden contain
in greater or smaller quantity, the most abundant mineral is cinnabar,
which is always crystalline and is often crystallized. The ores have,
besides, a small quantity of selenium and iron pyrites intimately
mixed with the cinnabar. The gangue is quartz, occasionally
argillaceous and bituminous. The following are assays of some of the
ores made by Escosura:
Metal. Requiebro. Vaciscos. China.
1 2 3 4 5 6 7 8
Cinnabar 29.1 21.2 13.3 10.2 5.1 2.8 1.2 0.86
Iron pyrites. 2.2 2.0 2.0 1.9 12.3 1.5 2.1 2.80
Bituminous matter 0.6 1.0 1.0 1.2 4.6 0.7 3.4 0.90
Gangue 67.5 74.8 82.1 76.5 77.5 93.3 90.2 93.50
---- ---- ---- ---- ---- ---- ---- -----
Total 99.4 94.0 98.8 98.9 99.5 98.3 98.7 98.06
Quicksilver 25.05 18.28 11.47 8.64 4.40 2.41 1.03 0.75
It appears to be a difficult matter to determine the average
percentage of the various grades of ore. In 1872, a commission
classified and sampled a lot of 300 tons with the following results:
Quantity, Per cent.
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