igneous
Basalt
Extrusive mafic igneous rock
Hardness: 6 on Mohs scale; Color: dark grey to black or brownish; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic); Specific gravity: 2.8-3.0.
- Hardness
- 6 on Mohs scale
- Color
- dark grey to black or brownish
- Luster
- dull to earthy
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Physical properties
Hardness: 6 on Mohs scale; Color: dark grey to black or brownish; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic); Specific gravity: 2.8-3.0.
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.
Uses & applications
Widely used in construction as aggregate for concrete, asphalt, and road base; occasionally used in high-quality architectural tiles or statues.
Geological facts
Basalt is the most common rock on Earth's surface and makes up most of the ocean floor. It is also common on the Moon and Mars.
Field identification & locations
Identify by its heavy weight (high density), dark color, and lack of visible individual crystals. Common in volcanic regions like the Pacific Northwest or Hawaii.
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Dark Igneous Rock (Likely Basalt or Diabase)
Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.
Igneous
Magnetite
Iron(II,III) oxide (Fe3O4)
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Blue Apatite
Apatite (Group), Ca5(PO4)3(F,Cl,OH)
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Sodalite
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Magnetite
Magnetite (Fe3O4)
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