igneous
Basalt with Quartz/Calcite Veins
Extrusive mafic igneous rock with hydrothermal mineralization
Hardness: 5-6 (base rock), 7 (veins); Color: dark gray to black matrix with white/yellowish veins; Luster: dull to earthy (matrix), vitreous (veins); Structure: fine-grained (aphanitic); Cleavage: none (conchoidal fracture).
- Hardness
- 5-6 (base rock), 7 (veins)
- Color
- dark gray to black matrix with white/yellowish veins
- Luster
- dull to earthy (matrix), vitreous (veins)
Identified More igneous →
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Physical properties
Hardness: 5-6 (base rock), 7 (veins); Color: dark gray to black matrix with white/yellowish veins; Luster: dull to earthy (matrix), vitreous (veins); Structure: fine-grained (aphanitic); Cleavage: none (conchoidal fracture).
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. The veins formed later through hydrothermal activity where mineral-rich hot water filled cracks in the solidified basalt.
Uses & applications
Basalt is used extensively in construction (aggregate, pavement), while veined specimens are popular as decorative stones and for educational geological collections.
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
Identified by its heavy weight, dark color, and fine texture. Veins indicate post-volcanic tectonic or hydrothermal stress. Commonly found in volcanic fields, oceanic islands, and mid-ocean ridges.
