It is not an easy matter to explain the classification of the ore at Almaden. _Metal_ is there called the richest mineral, composed of quartz impregnated with crystalline cinnabar. _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. Average of Grade. No. kilos. mercury. grade. Metal { 1. 81,890 23.86 } { 2. 14,970 22.65 } 24.80 Requiebro { 3. 12,240 15.20 } { 4. 17,000 10.50 } 12.47 China { 5. 31,890 3.84 } { 6. 32,360 1.17 } 1.75 { 7. 28,960 0.10 } Vaciscos 8. 78,320 9.24 9.24 This general average of 12.28 per cent. of mercury is pronounced higher than the usual run of the ore, which, it is stated, does not go above 7 to 8.50 per cent.