Colored gemstones embark on long, incredible journeys before they make their homes in beautiful jewelry: It is only through a chance combination of tremendous heat, pressure, and a great deal of time that some of the world's most vibrant treasures are initially formed. Magma from deep within the earth rises towards the earth's crust, cooling in the process. Sometimes, this magma crystallizes and forms minerals. Then, overwhelming subterranean pressure subtly alters the chemical makeup of these minerals. This variable force, combined with the presence or absence of other factors like air and water, results in the formation of a wide variety of gemstones waiting to be mined.