Basalt
Rock made of plagioclase, pyroxene
Common
A fine-grained, dark grey to black volcanic rock: more than nine tenths of all volcanic rock on Earth. Its runny lava spreads over great areas and piles up into flood basalts, often cracked into columns as it cools.
Rock
- Kind of rock
- Volcanic igneous rock
- Rock family
- Volcanic rock
- Texture
- fine-grained (crystals too small to see), porphyritic (large crystals in a fine groundmass)
- Also contains
- Olivine, Magnetite, Ilmenite
- Deposits
- Volcanogenic massive sulfide deposit
- Shapes the land into
- Plateau, Volcanic Field
- How it forms
- Lava rich in magnesium and iron, from the upper mantle, cools quickly at or near the surface.
- Uses
- Building blocks, groundwork, cobblestones cut from its columns, statues, and stone wool insulation.
Crystallography
- Habits
- Massive, Columnar
Physical properties
- Density
- 2.9 g/cm³
- Luster
- Dull
- Colors
- dark gray, black
- Transparency
- Opaque
Geology
- Origins
- Volcanic
- Geography
- worldwide, India (Deccan Traps), USA (Columbia River Plateau), Russia (Siberian Traps), Brazil (Paraná Traps)
Classification
- Rarity
- Common
- Gem quality
- No
Sources
- Basalt. 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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