because Emerald crystals are formed in metamorphic rocks, whereas other
beryls grow in pegmatites. Metamorphic transformation generally limits
the size of Emerald crystal formation, making them even rarer in larger
sizes. Emeralds derive their green hue from minute traces of chromium
locked within the stone's cyclosilicate crystals - the same Midas element
which gives rubies their fiery redness. "With less than one percent
chromium (or vanadium), an Emerald's crystal lattice passes the green
portion of white light while absorbing the red and blue."
Emeralds are found in several places on the planet. Without a doubt, the finest Emeralds come from the top three Colombian mines: Muzo, Chivor, and Cosquez. Emeralds of varying (but generally inferior) color, clarity, and quality are also mined in Brazil, Pakistan, Afghanistan, Madagascar, Nigeria, Russia, Zambia, and Zimbabwe.
Colombian Emeralds set the color and quality standards for Emeralds. Additionally, most of Colombia's gems are cut within the country. Fine Colombian Emeralds enjoy a rarity which places them among the" highest investment values of all gems." Emeralds are weighed in carats (not to be confused with karats, which refers to the purity of gold), with one carat equaling 1/5 gram, or 1/42 ounce. Because of the relatively low specific gravity of Emeralds (SGE = 2.72), Emeralds are physically larger than similarly weighted diamonds or rubies.