igneous
Basalt
Basalt (Aphanitic Mafic Igneous Rock)
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Earthy, Crystal Structure: Aphanitic (fine-grained), Specific Gravity: 2.8–3.0
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Physical properties
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Earthy, 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 at the Earth's surface. Common in oceanic crust and volcanic regions.
Uses & applications
Used extensively in construction as aggregate, road base, and concrete. Also used for high-temperature stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It also exists on the Moon (Maris) and Mars.
Field identification & locations
Identify by its heavy weight, dark color, and lack of visible crystals. Commonly found in former volcanic fields or riverbeds near lava flows.
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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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