igneous
Basalt with vesicles/amygdules
Basalt (containing volcanic glass and plagioclase)
Hardness: 6-7 (Mohs); Color: Dark grey to black with light tan/white inclusions; Luster: Dull to vitreous; Structure: Aphanitic with vesicular or amygdaloidal texture; SG: 2.8-3.0
- Hardness
- 6-7 (Mohs)
- Color
- Dark grey to black with light tan/white inclusions
- Luster
- Dull to vitreous
Identified More igneous →
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Physical properties
Hardness: 6-7 (Mohs); Color: Dark grey to black with light tan/white inclusions; Luster: Dull to vitreous; Structure: Aphanitic with vesicular or amygdaloidal texture; SG: 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. The lighter spots (amygdules) are formed when gas bubbles (vesicles) are filled by secondary minerals like quartz or calcite over time.
Uses & applications
Used in construction (crushed stone), road base, concrete aggregate, and decorative landscaping.
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 (high density), and fine-grained texture. Often found in volcanic regions or as rounded river/beach stones. Collectors look for unique amygdaloidal patterns.
