igneous
Basalt
Mafic volcanic rock (primarily Pyroxene and Plagioclase feldspar)
Hardness: 6 Mohs; Color: dark grey to black; Luster: dull/earthy; Crystal structure: fine-grained (aphanitic) or porphyritic; Specific gravity: 2.9-3.1
- Hardness
- 6 Mohs
- Color
- dark grey to black
- Luster
- dull/earthy
Identified More igneous →
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Physical properties
Hardness: 6 Mohs; Color: dark grey to black; Luster: dull/earthy; Crystal structure: fine-grained (aphanitic) or porphyritic; Specific gravity: 2.9-3.1
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon. Most basalt flows are from the Cenozoic era.
Uses & applications
Extensively used in construction for road base, concrete aggregate, railroad ballast, and dimension stone for paving.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is juga found on the Moon and Mars in the form of 'Maria'.
Field identification & locations
Identify by its dark color, heavy weight (high density), and lack of visible individual crystals without magnification. Found globally in volcanic regions like Hawaii, Iceland, and the Deccan Traps.
