Monday, November 11, 2013

Ore Shoots

Chemically formed ore shoots can also yield very good ore deposits. During vein formation, hot quartz-rich, acidic fluids will react with rocks of favorable chemistry, particularly rocks with calcium carbonate (limestone). Thus following a vein in any area that may have limestone should lead any prospector to search the limestones for gold and other valuable minerals. Replacement deposits and skarns are often formed when such mineralizing fluids come in contact with limestone or even rocks such as limy shales, or limy sandstones. In some cases, the replacement deposits can be very rich.
Cupriferous gossan - note the tawny limonite (hydrated iron oxide) with fissures filled with azurite (copper carbonate) typically found in many mining districts in Arizona and Utah.