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Ralstonite

Named for Reverend J. Grier Ralston of Pennsylvania, USA, who was the first to observe the mineral. It occurs in granite pegmatites that are fluorine bearing as well as in antimony deposits of hydrothermal origin within silicified limestone. Quite a few localities including in Greenland, the USA, Bolivia, Australia, Norway, Italy, Ukraine, Kazakhstan, Russia, and others.
Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/ralstonite.pdf
- Formula
- Na0.5(Al,Mg)2(F,OH)6·H2O
- Crystal System
- Isometric
- Cleavage
- Perfect, Perfect, Perfect
- Luster
- Vitreous - Greasy
- Color
- colorless, white
- Streak
- white
- Class
- Isometric - Hexoctahedral
- Fracture
- Brittle - Uneven
- Hardness
- 4.5
- WebMineral
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- Mindat
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Ralstonite from Ivigtut mine, Arsuk Fjord, Sermersooq, Greenland

Colorless, but stained by iron, octahedral crystals of Ralstonite to 2mm.