Definitions

beryl

beryl

[ber-uhl]
beryl, mineral, a silicate of beryllium and aluminum, Be3Al2Si6O18, extremely hard, occurring in hexagonal crystals that may be of enormous size and are usually white, yellow, green, blue, or colorless. Beryl is commonly used as a gemstone. The refractive index is low, and the stones have little or no fire. The most valued variety of beryl is emerald. An aquamarine is a blue to sea-green beryl; morganites are rose-red beryls. It is the principal raw material for the element beryllium and its compounds.

Mineral composed of beryllium aluminum silicate, Be3Al2(SiO3)6, a commercial source of beryllium. Several varieties are valued as gemstones: aquamarine (pale blue-green); emerald (deep green); heliodor (golden yellow); and morganite (pink). Before 1925 beryl was used only as a gemstone, but since then many important uses have been found for beryllium (e.g., in nuclear reactors, space vehicles, and X-ray tubes). No large deposits have been found, and most production is a by-product of the mining of feldspar and mica. Brazil is a major producer; others include Zimbabwe, South Africa, Namibia, and the U.S.

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The mineral beryl is a beryllium aluminium cyclosilicate with the chemical formula Be3Al2(SiO3)6. The hexagonal crystals of beryl may be very small or range to several meters in size. Terminated crystals are relatively rare. Beryl exhibits conchoidal fracture, has a hardness of 7.5–8, and a specific gravity of 2.63–2.80. It has a vitreous luster and can be transparent or translucent. Its cleavage is poor basal and its habit is dihexagonal bipyramidal. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, red, and white. The name comes from the Greek beryllos which referred to a precious blue-green color of sea water stone. The term was later adopted for the mineral beryl more exclusively.

Varieties

Varieties of beryl have been considered gemstones since prehistoric times. Recognized for its beauty, in the Bible, in Ezekiel 1:16, the wheels of God's throne are described as having the appearance of "gleaming beryl."

Colorless beryl is called goshenite, pink beryl is morganite, red beryl is bixbite or "red emerald" or "scarlet emerald," clear bright yellow beryl is "golden beryl," yellow-green beryl is heliodor, green beryl is emerald, blue beryl is aquamarine, and deep blue beryl is maxixe. Red beryl is extremely rare. Usually gems are under a carat, are only used in very special jewelry. It is mined primarily in Utah. Blue beryl (aquamarine) will not fade in color when exposed to sunlight. Maxixe is a deep blue stone that fades to white when exposed to sunlight or is subjected to heat treatment, though the color returns with irradiation. Other, unnamed shades such as honey yellow are also known.

Deposits

Beryl of various colors is found most commonly in granitic pegmatites, but also occurs in mica schists in the Ural Mountains, and limestone in Colombia. Beryl is often associated with tin and tungsten ore bodies. Beryl is found in Europe in Norway, Austria, Germany, and Ireland, as well as Brazil, Colombia, Madagascar (especially morganite), Russia, South Africa, the United States, and Zambia. U.S. beryl locations are in California, Colorado, Idaho, New Hampshire, North Carolina, South Dakota, and Utah.

The most famous source of emeralds in the world is at Muzo and Chivor, Boyacá, Colombia, where they make a unique appearance in limestone. Emerald are also found in the Transvaal, South Africa; Minas Gerais, Brazil; Zambia, and near Mursinka in the Urals in Russia. In the United States, emeralds are found in North Carolina.

New England's pegmatites have produced some of the largest beryls found, including one massive crystal with dimensions 5.5 m by 1.2 m (18 ft by 4 ft) with a mass of around 18 metric tons; it is New Hampshire's state mineral. As of 1999, the largest known crystal of any mineral in the world is a crystal of beryl from Madagascar, 18 metres long and 3.5 metres in diameter.

Applications

Massive beryl is a primary ore of the metal beryllium.

References

  • Sinkankas, John, 1994, Emerald & Other Beryls, Geoscience Press, ISBN 0-8019-7114-4
  • Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York ISBN 0-471-80580-7
  • Minerals.net
  • Mineral Galleries

See also

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