CS Book 1 _AS-2 Mining:Formation.pdf

Gemstone Formation and Mining KEY CONCEPTS Rocks are the raw materials of gemstone formation. Mining economics are affected by demand, political climate,...

Gemstone Formation and Mining KEY CONCEPTS Rocks are the raw materials of gemstone formation. Mining economics are affected by demand, political climate, labor costs, environment, accessibility, type of deposit, and Most colored stones form in the earth’s continental crust. mining methods. Geological conditions during mountain building are favorable An understanding of gemstone formation helps prospectors for gem formation. pick the right places to look for gems. In most igneous rocks, large crystals indicate slow cooling, Thousands of tons of eroded rock might yield only a few while small crystals indicate rapid cooling. ounces of gem material. Some types of volcanic rock can transport existing gems from Secondary deposits are easier to work than primary ones and deep in the crust to the earth’s surface. might contain greater concentrations of gems. Some of the largest and most perfect gem crystals come from Only the toughest gems survive to become part of secondary pegmatites. deposits. Superheated, pressurized water can transfer elements in solution and redeposit them in veins to form gems. 85