igneous
Basalt with Quartz Veining
Mafic Igneous Rock (primarily Plagioclase and Pyroxene) with SiO2 inclusions
Hardness: 6-7 Mohs; Color: Dark grey to black with white linear streaks; Luster: Dull/Matte (rock) to Vitreous (vein); Structure: Fine-grained/Aphanitic; Cleavage: None
- Hardness
- 6-7 Mohs
- Color
- Dark grey to black with white linear streaks
- Luster
- Dull/Matte (rock) to Vitreous (vein)
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Physical properties
Hardness: 6-7 Mohs; Color: Dark grey to black with white linear streaks; Luster: Dull/Matte (rock) to Vitreous (vein); Structure: Fine-grained/Aphanitic; Cleavage: None
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. The white veins are typically quartz or calcite that precipitated into fractures from hydrothermal fluids long after the rock cooled.
Uses & applications
Commonly used as construction aggregate, road base, and in river rock landscaping. Small polished pieces are used as massage stones or pocket charms.
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 heavy weight (high density), dark color, and fine-grained texture. Found along coastlines, riverbeds, and volcanic fields. Collectors look for unique vein patterns created by seismic activity.
