igneous
Basalt with Quartz Veins
Mafic Igneous Rock with Quartz (SiO2) intrusions
Hardness: 6-7 (basalt) and 7 (quartz); Color: Charcoal gray/black with white veins; Luster: Dull/earthy matrix with glassy (vitreous) veins; Structure: Microcrystalline; Cleavage: None/Conchoidal.
- Hardness
- 6-7 (basalt) and 7 (quartz)
- Color
- Charcoal gray/black with white veins
- Luster
- Dull/earthy matrix with glassy (vitreous) veins
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Physical properties
Hardness: 6-7 (basalt) and 7 (quartz); Color: Charcoal gray/black with white veins; Luster: Dull/earthy matrix with glassy (vitreous) veins; Structure: Microcrystalline; Cleavage: None/Conchoidal.
Formation & geological history
Basalt forms from the rapid cooling of magnesium-rich and iron-rich lava. The white veins are formed later by hydrothermal activity, where mineral-rich hot water flows through cracks, depositing quartz or calcite.
Uses & applications
Commonly used as construction aggregate, road base, and decorative river stones. Smooth water-worn specimens like this are popular in aquariums, zen gardens, and as pocket stones.
Geological facts
The contrasting patterns on these rocks are often referred to as 'lightning stones' or 'wishing stones' in folklore, specifically when a single white line wraps all the way around the circumference.
Field identification & locations
Identify by its heavy weight (high specific gravity), dark fine-grained texture, and hard white veins that cannot be scratched by a steel knife. Frequently found on beaches or in riverbeds where erosion has rounded the stone.
