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BERYL [ Silicates : Cyclosilicates ]

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Be3Al2(SiO3)6, Berylium aluminium Silicate: Gemstone, mineral specimens and source of beryllium

Beryl is often unknown to the general public, even the gemstone-buying public. However, it is one of the most important gem minerals. Beryl is colourless in pure form; it is the many different impurities that give beryl its varied colouration. Without these splendid colour varieties, beryl would be a rather ordinary gemstone with only average fire and brilliance. Emerald is the green variety and aquamarine is the blue variety of beryl.

emerald is highly prized and is one of the most valued gemstones. Its green colour is peerless and all other green gemstones are compared to its intensity. Emerald specimens are often “flawed” with mineral inclusions and fractures; unlike other gems, these are considered part of the stones’ “character.” These flaws actually help determine natural from synthetically-produced stones. Uncut emerald specimens are rare on the mineral markets, probably because even low grade emeralds can carry a high price when cut as gems. Especially hard to find are true “in-matrix” specimens. Fakes are often produced with natural crystals glued into a “host” rock and then sold as an in-matrix specimen with a highly inflated price.

aquamarine is also a popular gem although it does not command nearly as high a price as its green cousin. Uncut aquamarines are plentiful but relatively expensive, as would be expected of crystalline gemstone specimens. Large crystals of aquamarine are available on the open market and represent perhaps the largest raw gemstone specimens.

Physical Characteristics

Colour: varied and includes emerald green, blue to blue-green, yellow, greenish-gold, red, colourless and pink
Luster: vitreous
Transparency: Crystals are transparent to translucent
Crystal System: hexagonal; 6/m 2/m 2/m
Crystal Habits: typically include the hexagonal prism with pincoid terminations. The terminations are often modified by many different pyramidal faces which can sometimes produce a rounded termination in the rough shape of a used pencil eraser
Cleavage: imperfect in one direction (basal)
Fracture: conchoidal
Hardness: 7.5 – 8
Specific Gravity: approx. 2.6 – 2.9 (average)
Streak: white
Other: Faces on large crystals are often pitted, striated lengthwise and rough
Associated Minerals: include micas, quartz, euclase, calcite, tourmalines and some feldspars
Major Occurrences: include Colombia and some African localities for emerald; Brazil, Russia and Pakistan for aquamarine; California, Brazil, Africa, and many other localities for other beryls
Best Indicators: crystal habit, lack of good cleavage, hardness and colour
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