Gabbro
Rock made of pyroxene, plagioclase
Common
The coarse-grained twin of basalt, dark and heavy, of pyroxene and calcium-rich plagioclase. Much of the ocean floor is gabbro; the stone trade sells it as "black granite", though it is hard to work.
Rock
- Kind of rock
- Plutonic igneous rock
- Rock family
- Volcanic rock
- Texture
- coarse-grained
- Also contains
- Hornblende, Olivine
- How it forms
- Mafic magma crystallises slowly deep underground, at mid-ocean ridges and in layered intrusions under continental volcanoes.
- Uses
- Dimension stone under the trade name black granite, limited by how hard it is to work.
Crystallography
- Habits
- Granular, Massive
Physical properties
- Luster
- Vitreous
- Colors
- black, dark gray, dark green
- Transparency
- Opaque
Geology
- Origins
- Igneous
- Geography
- worldwide, South Africa (Bushveld Complex), Scotland (Rum), USA (Stillwater, Montana), Canada (Muskox intrusion)
Classification
- Rarity
- Common
- Gem quality
- No
Sources
- Gabbro. 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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