Emerald

Description

A transparent, green Gemstone composed of beryllium aluminum silicate. The prismatic Beryl crystals get their green color from trace amounts of Chromium or Vanadium. Emeralds were produced from Cleopatra's mines in Egypt's eastern desert in ancient times, but these stones were often flawed with microscopic elongated bubbles. Later, Romans made glass imitations of the stones because emeralds were ranked third in value after diamonds and pearls. High quality emeralds were imported from Columbia by the Spanish from the 1500s. The Muzo region, near Bogota, is still the main source for high quality emeralds. Other current sources for emeralds are the Urals, Austria (Habachtal), Norway, Australia, Tanzania, Zambia (discovered in 1931, produced since 1967), Zimbabwe (Sandawana, since 1956), Pakistan, India, Afghanistan, and Brazil. Emeralds tend to be brittle and crack easily. Since 1934, synthetic emeralds have been made from aquamarine seed crystals with a high-pressure, high-temperature process. They are used in lasers, masers, and semiconductors.

Uncut emerald

Synonyms and Related Terms

green beryl; beryllium aluminum silicate; smaragd (Dan., Ned., Nor., Sven.); Smaragd (Deut.); esmeralda (Esp.); émeraude (Fr.); szmaragd (Pol.); esmeralda (Port.)

Other Properties

Hexagonal system with prismatic crystals usually striated lengthwise. Cleavage is poor in one direction. Weakly pleochroic.

Fracture = uneven to conchoidal. Luster = vitreous. Streak = colorless.

Natural stones may have inclusions. Synthetic emeralds appear opaque and dull red in UV light

Composition	Be3Al2SiO6
Mohs Hardness	7.5 - 8
Density	2.68-2.78
Refractive Index	1.57-1.60

Cut emeralds

Additional Information

° Michael O'Donoghue and Louise Joyner, Identification of Gemstones, Butterworth-Heinemann, Oxford, 2003

Comparisons

Properties of Common Gemstones

Authority

• Sue Fuller, Rocks and Minerals, DK Publishing, Inc., New York City, 1995

• Jack Odgen, Jewellery of the Ancient World, Rizzoli International Publications Inc., New York City, 1982

• A.Lucas, J.R.Harris, Ancient Egyptian Materials and Industries, Edward Arnold Publishers Ltd., London, 4th edition, 1962

• Yasukazu Suwa, Gemstones: Quality and Value, Volume 1, Sekai Bunka Publishing Inc., Tokyo, 1999 Comment: RI=1.577-1.583; Specific gravity=2.72

• Michael O'Donoghue and Louise Joyner, Identification of Gemstones, Butterworth-Heinemann, Oxford, 2003 Comment: Chivor emeralds:RI=1.571-1.574; 1.577-1.580; spec.grav.=2.67-2.71 Muzo emeralds:RI=1.576-1.580; 1.582-1.586; spec.grav.=2.71-2.72

• Wikipedia, the free encyclopedia, at http://www.wikipedia.com

• G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971

• Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993

• Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976

• Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997