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Name Origin | Idocrase is derived from Greek words idos and krasis, meaning mixed appearance, because idocrase crystal forms resemble those seen on other species |
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Chemical Formula | Ca19Al4Fe(Al, Mg, Fe)8Si18O70(OH, F)8 |
Color | Colorless, green (various shades), brown (various shades), yellow (various shades), red, brownish red, blue, blue green, pink, violet, sometimes color-zoned |
Hardness | 6 - 7 on Mohs Scale |
Crystal System | Tetragonal. Crystals often well formed, prismatic, pyramidal, often with complex modifications; granular, massive. Often inter-grown with grossular |
Cleavage | None. Fracture conchoidal |
Specific Gravity (SG) | 3.32 - 3.47 |
Luster | Vitreous to resinous |
Stone size |
Crystals up to several inches in length occur at a few locations, but these are seldom transparent except in small areas. The maximum expectable size for a faceted idocrase is in the order of 10 carats. |
Note: Idocrase (also known as Vesuvianite) is one of the lesser known and more beautiful collector gems. When properly cut it is as bright and attractive as the garnets which it so strongly resembles. The complexity of its chemistry lead to a huge range in properties and colors. Cuttable material is known from Italy (brown and green), Quebec (pale green, bright yellow), New York (brown), Pakistan (green), Kenya (brown and green).
References:
1- Color Encyclopedia of Gemstones, Joel E. Arem, VNR publications, New York.
Photo Credit:
www.shutterstone.com
"Vesuvian" by Ra'ike (see also: de:Benutzer:Ra'ike) - Own work. Licensed under CC BY 2.5 via Commons - https://commons.wikimedia.org/wiki/File:Vesuvian.jpg#/media/File:Vesuvian.jpg
1- Color Encyclopedia of Gemstones, Joel E. Arem, VNR publications, New York.
Photo Credit:
www.shutterstone.com
"Vesuvian" by Ra'ike (see also: de:Benutzer:Ra'ike) - Own work. Licensed under CC BY 2.5 via Commons - https://commons.wikimedia.org/wiki/File:Vesuvian.jpg#/media/File:Vesuvian.jpg