igneous
Basalt
Basalt (composition of Plagioclase feldspar and Pyroxene)
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); 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. It is the most common volcanic rock on Earth.
Uses & applications
Used primarily in construction (crushed stone for road base, concrete aggregate, and railroad ballast), as well as in industrial floor tiles and cobblestones.
Geological facts
Basalt makes up almost the entire seafloor and is also the primary rock found on the Moon's maria (the dark plains), where it was formed by ancient lunar volcanic eruptions.
Field identification & locations
Identify by its dark color, heavy weight (density), and lack of visible crystals to the naked eye. Often found in volcanic regions, oceanic crust boundaries, and giant lava flood plains.
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Fluorapatite (Ca5(PO4)3F)
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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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Sodalite
Sodalite - Na8(Al6Si6O24)Cl2
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Blue Apatite
Apatite (Group), Ca5(PO4)3(F,Cl,OH)
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Magnetite
Magnetite (Fe3O4)
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