New Almaden hydrothermal deposition of cinnabar from deep within the earth is found in a gangue of silica-carbonate rock formed locally by hydrothermal alteration of serpentine. The Guadalupe mine produced about 10% as much mercury as the New Almaden. There are several smaller mines in the mining district, but their ore production was not significant. The only significant quicksilver ore is cinnabar; other sulfides are present in small quantities. Mining, other than a single placer deposit of cinnabar, was underground. There is a high probability of undiscovered high-grade ore which could be found and exploited using modern techniques. Mining operations resulted in
Ore shoot Ore shoot In mining and geology, an ore shoot is a long seam of mineral or metal bearing rock that can be profitable to extract. The term may have originated in the 17th and 18th centuries when various theories existed on the origins of ore deposits, including some that suggested they grew like trees. Tabular or sheet-like deposits of metalliferous ores often contain areas of enhanced metal content that are larger in one dimension than another. A structure may contain multiple ore shoots. A "vein," "lode" or other mineral-bearing structure could be thick, steeply inclined within the host rock, persisting