Mined for over 4000 years, the earliest emerald mines existed in Egypt near the Red Sea, the fabled mines of Cleopatra. Today these mines are of historical interest only; however, most emeralds found in ancient jewels generally come from this Egyptian locality. The most important modern mine is the Muzo mine in Colombia. First discovered by natives, then abandoned, then rediscovered in the 1700s, Muzo is where some of the most beautiful deeply saturated primarily bluish-green stones are mined from hydrothermal veins in the host rock. Chivor, Cosquez and Pena Blanca are other Colombian mines that produce world-class gems. Brazil, Zimbabwe, Zambia, Russia, Afghanistan and Pakistan are other nations that contain emerald deposits.
Emerald is the best known variety of the species Beryl, which includes Aquamarine (bluish-green, greenish-blue), Morganite (light orangish-pink, pink), Pizzotaite (reddish-pink), Bixbite (red), Heliodor (yellow) and Goshenite (colorless). In Colombian emerald, chromium, sometimes with vanadium, is the primary element responsible for the saturated green color, which range from bluish-green to green to yellowish-green. Emerald naturally contains inclusions, sometimes called “gardens” or “jardins.” These inclusion gardens are used as indications of the stones’ natural origin.
Zambian emeralds are quickly gaining notice and respect. These beautiful emeralds are mined from pegmatite formations and extracted from the emerald-bearing rock by controlled blasting and by hand using chisels so as not to damage the emerald material. Zambian emeralds generally contain fewer inclusions in comparison to Colombian emeralds, and the color is dark to light green with some beautiful and brilliant bluish green. A single polished gem quality Zambian emerald can go up to 60 carats. Large specimens have also been produced and are highly sought after by collectors due to their rarity.
Emerald is hard, at 7½ on the Mohs’ scale of hardness, so it can be used for most jewelry settings. Emeralds are typically oiled to help homogenize the color and seal inclusions. This treatment is perfectly acceptable and should be disclosed. Because of this oiling and the somewhat delicate nature of emeralds, they should not be exposed to a steam cleaner or ultra-sonic cleaner.
Emeralds over 4 carat, with deep saturated bluish-Green color, few inclusions, clean to the unaided eye, and have not been oiled or treated in any way, are extremely rare but do exist and can command extraordinary prices.
Notable emeralds include a 4½” tall vase in the Viennese treasury that is carved from a single emerald crystal and weighs 2,205 carats. Well-known collections of emeralds exist in the treasuries of Iran, India and Russia.
Variety: Emerald, Cats’ Eye Emerald, Star Emerald, Trapiche Emerald
Chemical Composition: Be3Al2(SiO3)6
Color: Green, Bluish-Green, Yellowish-Green
Hardness: 7½ - 8
Crystal System: Hexagonal
Refractive Index: 1.577 - 1.583 (+/- .017)
Specific Gravity: 2.72 (+.18, -.05)