Pegmatite
Rock made of quartz, feldspar, mica
Uncommon
An igneous rock of giant crystals, usually over a centimetre and sometimes over a metre, of quartz, feldspar and mica. Many of the largest crystals on Earth grew in pegmatites: feldspars of thousands of tons in Karelia, spodumene twelve metres long in the Black Hills.
Rock
- Kind of rock
- Plutonic igneous rock
- Rock family
- Granite
- Texture
- very coarse (crystals over a centimetre)
- Also contains
- Beryl, Tourmaline, Spodumene, Apatite, Garnet, Albite
- Deposits
- Pegmatite deposit
- How it forms
- The last fluid of a crystallising magma body, rich in water and rare elements and very runny, lets a few crystals grow huge instead of many small ones.
- Uses
- Complex pegmatites are mined for lithium, beryllium, tin, tantalum, niobium, rare earths and gems.
Crystallography
- Habits
- Granular, Massive
Physical properties
- Luster
- Vitreous
- Colors
- white, pink, gray
- Transparency
- Opaque
Geology
- Origins
- Igneous
- Host rocks
- Granite
- Geography
- worldwide, Russia (Karelia), USA (Black Hills, South Dakota)
Classification
- Rarity
- Uncommon
- Gem quality
- No
Sources
- Pegmatite. Wikipedia.
- M. R. Gillespie, M. T. Styles, BGS Rock Classification Scheme, Volume 1: Classification of igneous rocks (Research Report RR 99-06). British Geological Survey, 1999.
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