(beryllium aluminium meta-silicate) has the formulae Be3Al2Si16O18 and a relative hardness of 8. It has a characteristic six-sided outline and is used as a gem stone of various colours, its green variety being emerald. Beryl is also the major source of the rare element beryllium, a light metal similar to aluminum. Beryl is quite common and occurs usually in granite rocks, mica schists and with tin ores.
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