Emerald

March 1, 2016

Emerald is the valuable bright green variety of the mineral beryl. It is often found in granites and pegmatites (rocks with coarse – very coarse grains). The bright green colouring of emerald is due to the presence of chromium and vanadium. Pure beryl is colourless and can also turn blue/green or yellow/green due to the presence of iron. This colouring depends on the state of oxidation of the iron impurities.   Emerald crystals may form via hydrothermal processes where hot, hydrothermal fluids escape from magma deep in the earth’s crust and begin to cool in the fractures/cracks of previously existing bed rock. For this process to occur, the hydrothermal fluids must be rich in beryllium. The majority of emeralds mined in Columbia are formed via hydrothermal processes.   The other common way that emeralds are formed, are as pegmatite deposits. These form when molten magma rises and begins to cool. Certain minerals form faster than others as the magma cools, so the remaining solution will be rich in beryllium, concentrating the emeral