Wednesday, April 1, 2009

April 2009 Mineral of the Month


The name beryl may possibly come from the greek word 'beryllos' which refers to a number of blue-green stones in antiquity. This precious gemstone mineral occurs as prismatic crystals which are sometimes terminated with small pyramids. The crystals are often striated parallel to their length and may be of massive size. Specimens up to eighteen feet long have been recorded. It also forms in massive, compact and columnar habits. The color varies greatly and gives rise to named varieties one might recognize such as Emerald, Morganite, Heliodor, Goshenite and Aquamarine. There is also a variety in red that was once referred to as Bixbite but has since been proved to be incorrect. This red variety is referred to as Red Beryl. Beryl is a member of the silicates group. Its chemical composition is Be3AI2SI6O18. It is quite durable coming in at 7-8 on the Mohs Scale. It is transparent to translucent with a vitreous luster. It has a white streak. Its specific gravity is 2.6 to 2.9. It has an indistinct cleavage with and uneven to conchoidal fracture.

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.