igneous
Basalt River Stone
Aphanitic Mafic Igneous Rock
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull or matte; Crystal structure: Aphanitic (fine-grained, crystals not visible to the naked eye); Specific Gravity: 2.8-3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black
- Luster
- Dull or matte
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull or matte; Crystal structure: Aphanitic (fine-grained, crystals not visible to the naked eye); 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 specific specimen has been rounded and smoothed by fluvial or coastal erosion.
Uses & applications
Commonly used as decorative garden stones, in hot stone massage therapy, as structural aggregate in construction, and for paving.
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 extensively on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size (high density), and lack of visible crystals. Commonly found in riverbeds, beaches, and volcanic fields.
