igneous

Basalt

Mafic Igneous Rock

Hardness: 6-7 (Mohs scale); Color: Dark grey to black; Luster: Dull/earthy; Crystal structure: Aphanitic (fine-grained); Cleavage: Non-existent; Specific Gravity: 2.8 - 3.0

Hardness: 6-7 (Mohs scale)
Color: Dark grey to black
Luster: Dull/earthy

Identified April 8, 2026More igneous →

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Physical properties

Hardness: 6-7 (Mohs scale); Color: Dark grey to black; Luster: Dull/earthy; Crystal structure: Aphanitic (fine-grained); Cleavage: Non-existent; Specific Gravity: 2.8 - 3.0

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the surface of a terrestrial planet or a moon.

Uses & applications

Used primarily in construction (crushed stone, concrete aggregate), road base, and as high-quality building stone or paving sets.

Geological facts

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. Large parts of the Moon and Mars are also covered in basaltic plains.

Field identification & locations

Identify by its dark color, heavy weight (density), and lack of visible crystals. It is commonly found in volcanic regions and on beaches where volcanic activity occurred.

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

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