Friday, May 16, 2014

Precious Beryl

The title Precious Beryl refers to all colors of beryl that are not emerald or aquamarine (previous blogs). Beryl is a high temperature and high pressure metamorphic mineral. The colors in precious beryl are caused by different impurities included in the chemical makeup of the crystal. All forms of precious beryl have the same basic properties:
Color: yellow, gold, yellow-green, pink, red and colorless
Streak Color: white (usually only rough is tested for streak)
Moh's hardness: 7 1/2 to 8
Cleavage: indistinct
Fracture: conchoidal (like the bulls eye in glass when shot by a BB)
Refractive Index: 1.562 - 1.602
These forms are:
Illustration 1: Bixbite/Red Beryl
 
Bixbite (Red Beryl): probably the rarest gemstone, found in a rasberry red color, the mineral is Bixbite, the gemstone is usually called Red Beryl. Some gemologists include red beryl as being a sub-group of Morganite.
Bixbite photo Bixbite.jpg
Golden Beryl: color varies from lemon to golden yellow; Heliodore is frequently included as a subgroup. Inclusions are rare.
Golden Beryl photo GoldenBeryl.jpg
Goshenite: named after a type locality in Goshen, MA (USA); this is the "white" / colorless variety of beryl. Goshenite can be used as a diamond simulant.
Goshenite photo Goshenite.jpg
Morganite: also called pink beryl, this stone was named after financier J.P. Morgan.
Morganite photo Morganite-1.jpg
Because of the large variety of color, precious beryl can be confused with other colored stones (all gemstones other than diamond are called colored stones). Some greenish beryls can be heated and will change in color to blue (aquamarine).

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