Density: 2.63-2.80g/cm³
Formula of Beryl: Be₃Al₂Si₆O₁₈
Hardness - 7.5 to 8 mohs
Molar Mass: 537
Specific gravity - 2.65 to 2.85

Emeralds are the premier gems in the beryl family. For more than 4,000 years, emeralds have been among the most valuable of all jewels. In one of the rare cases where lore and fact coincide, emerald history really does begin in Egypt, where there actually was a "Cleopatra's Mine." Mining in the desert south of Cairo near the Aswan Dam began before 2000 B.C. and continued until about 1200 A.D. Although emeralds were extracted for 2000 years before Cleopatra was born, her use and love of gems led to her name being attached to the mine, an association that remains. Egypt supplied the known world with emeralds throughout the Biblical period and through the Middle Ages. But most of the stones, as you see in numerous examples in Fred Ward's book on emeralds, would barely be classified as gems today. The world had to wait until Spain conquered the New World and found Indians wearing great emeralds to see how fine the green gemstones could be.

Fabulous emerald crystals came from what is now Colombia. It took Spain five decades to overpower the Muzo Indians who occupied the mining area. Monarchs and the gem-loving royalty in India, Turkey, and Persia sought the New World treasures once the gems arrived in Europe. The new emerald owners produced spectacular artifacts between 1600 and 1900.

Today Colombia, Brazil, and Zambia mine most commercial emeralds. Several other countries, such as Pakistan and Zimbabwe, mine smaller amounts. Although Brazil produces more emeralds annually than any other country, Colombia dominates the trade by setting the standards for size and color. It is Colombian emeralds against which all others are judged. Rarer and sometimes more expensive than a similar-sized diamond, Colombian emeralds have a unique look, a green lightly touched with blue. Muzo, the original mine, remains the most important emerald mine in the world.