igneous
Basalt (with possible Calcite/Quartz veining)
Afanitic Mafic Igneous Rock
Hardness: 5-6 (Mohs); Color: Dark grey to black; Luster: Dull/Submetallic; Crystal Structure: Fine-grained (aphanitic); Specific Gravity: 2.8–3.0
- Hardness
- 5-6 (Mohs)
- Color
- Dark grey to black
- Luster
- Dull/Submetallic
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey to black; Luster: Dull/Submetallic; 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 at or very near the Earth's surface. This specimen appears to have secondary mineral infilling (veins) in fractures.
Uses & applications
Commonly used in construction as aggregate (crushed stone), for paving, and in the manufacturing of rock 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 is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and fine-grained texture. Found globally in volcanic regions and oceanic crust plates.
