igneous
Basalt
Vesicular Basalt
Hardness: 5-6 Mohs. Color: dark gray, black, or greenish-black. Luster: dull to earthy. Texture: fine-grained (aphanitic) with small holes called vesicles. Crystal structure: microcrystalline to glassy.
- Hardness
- 5-6 Mohs
- Color
- dark gray, black, or greenish-black
- Luster
- dull to earthy
Identified More igneous →
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Physical properties
Hardness: 5-6 Mohs. Color: dark gray, black, or greenish-black. Luster: dull to earthy. Texture: fine-grained (aphanitic) with small holes called vesicles. Crystal structure: microcrystalline to glassy.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava (mafic lava) at or very near the Earth's surface. The holes (vesicles) were formed by gas bubbles trapped in the lava during solidification.
Uses & applications
Used extensively in construction for road base, concrete aggregate, and railroad ballast. Also used as decorative landscaping stone and occasionally in jewelry for 'lava rock' beads.
Geological facts
Basalt is the most common rock in Earth's crust and makes up the majority of the ocean floor. It is cũng the primary rock found on the Moon (the dark lunar maria) and Mars.
Field identification & locations
Identify in the field by its dark color, heavy weight (high density), and fine-grained texture. Commonly found in volcanic regions like Iceland, Hawaii, and the Pacific Northwest.
