Beryl is a relatively rare silicate mineral with a chemical composition of Be3Al2Si6O18. It is found in igneous and metamorphic rocks in many parts of the world. Before 1969, beryl served as the only important ore of beryllium metal. Since then, most of the world's supply of beryllium is refined from bertrandite, a beryllium silicate hydroxide, mined at Spor Mountain, Utah. Small amounts of beryl, mostly produced as a by-product of gemstone mining, are still used to produce beryllium.

The major economic interest in beryl today is its use as a gemstone. It is one of the most important gem minerals, and the gems are named by their color as emerald (green), aquamarine (greenish blue to blue), morganite (pink to orange), red beryl (red), heliodor (yellow to greenish yellow), maxixe (deep blue), goshenite (colorless), and green beryl (light green). Emerald and aquamarine are the most popular. Compared to other gemstones, emeralds are second only to diamonds in terms of the dollar value imported into the United States. Occasionally, chatoyant specimens of beryl are found that can be cut into cabochons to produce interesting cat's-eye gemstones.

Aquamarine berly: A spectacular crystal of auamarine from the Shigar Valley of northern Pakistan.

Geologic Occurrence of Berly

Beryl is a mineral that contains a significant amount of beryllium. Beryllium is a very rare metal, and that limits the occurrence of beryl to a few geological situations where beryllium is present in sufficient amounts to form minerals. It mainly occurs in granite, rhyolite, and granite pegmatites; in metamorphic rocks associated with pegmatites; and, in veins and cavities where hydrothermal activity is associated with rocks of granitic composition. These different types of deposits are often found together and serve as an exploration model for finding beryl.

Beryl is also found where carbonaceous shale, limestone, and marble have been acted upon by regional metamorphism. The famous emerald deposits of Colombia and Zambia have been formed under these conditions. The carbonaceous material is thought to provide the chromium or vanadium needed to color the emerald.

Physical Properties of Berly

The most important physical properties of beryl are those that determine its usefulness as a gem. Color and clarity are very important. Beryl occurs in a diversity of colors, with some of those colors being highly desirable. It also occurs in transparent crystals that have clarity and size that are sufficient for faceting. Many beryls have a color that can be improved by heating.

Beryl's durability is generally good. It has a Mohs hardness of 7.5 to 8, which helps it resist scratches when worn in jewelry. Beryl breaks by cleavage and it is also brittle. Many specimens, especially of emerald, are fractured or highly included. These weaknesses can make it vulnerable to damage by impact, pressure or temperature change.

Physical Properties of Beryl

Chemical Classification Silicate
Color Green, yellow, blue, red, pink, orange, colorless
Streak Colorless (harder than the streak plate)
Luster Vitreous
Diaphaneity Translucent to transparent
Cleavage Imperfect
Mohs Hardness 7.5 to 8
Specific Gravity 2.6 to 2.8
Diagnostic Properties Crystals are prismatic with flat terminations, hexagonal, and without striations. Hardness and relatively low specific gravity.
Chemical Composition Be3Al2Si6O18
Crystal System Hexagonal (occurs in prismatic to tabular crystals)
Uses Gemstones, a minor ore of beryllium.

Beryl can be difficult to identify. When it occurs as a crystal, its prismatic, hexagonal form with flat terminations and lack of striations is a good aid in identification. Beryl's high hardness and relatively low specific gravity can be helpful for identifying massive specimens.

Uses of Beryl (ore of beryllium)

Beryl was once the only important ore of beryllium metal, but today the mining of bertrandite at Spor Mountain, Utah supplies about 80% of the world's beryllium. The extraction of beryllium from beryl is very costly, and as long as bertrandite is available in large amounts, beryl will be a minor ore of that metal.


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