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ore - Encyclopedia.com |
 | | Nearly all rock deposits contain some metallic minerals, but in many cases the concentration of metal is too low to justify mining the ore. Ores are usually found concentrated in deposits with a definite gradation of metal concentration from the ore to the surrounding rock. |
 | | Veins of ore exposed to weathering are often eroded and redeposited in placers and alluvial deposits, e.g., ore-bearing stream and lake gravels or beach sands. |
 | | Important ores of aluminum, iron, manganese, and tin are oxides; important ores of antimony, copper, lead, mercury, nickel, silver, and zinc are sulfides. |
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