igneous
Basalt with Quartz Vein
Basalt (SiO2 vein inclusion)
Hardness: 6-7 on Mohs scale; Color: Dark grey to charcoal/greenish matrix with a white/tan linear vein; Luster: Dull/earthy matrix with slightly vitreous vein; Structure: Fine-grained aphanitic matrix; Cleavage: None (conchoidal fracture).
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull/earthy matrix with slightly vitreous vein
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Dark grey to charcoal/greenish matrix with a white/tan linear vein; Luster: Dull/earthy matrix with slightly vitreous vein; Structure: Fine-grained aphanitic matrix; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the Earth's surface. The distinctive line is a secondary mineral vein, likely quartz or calcite, formed when mineral-rich hydrothermal fluids filled a crack in the rock and crystallized over time.
Uses & applications
Common basalt is used in construction as aggregate, road base, and railroad ballast. Naturally rounded river stones like this specimen are frequently used in decorative landscaping, zen gardens, and as 'worry stones' or massage stones.
Geological facts
The single band running around the rock is often called a 'Wishing Stone' in folk tradition. Geologically, it represents the intersection of two distinct geological events: the initial volcanic eruption and a subsequent fracturing/filling event.
Field identification & locations
Identified in the field by its dark, heavy, fine-grained texture and the presence of a continuous, contrasting mineral band. Commonly found in riverbeds, glacial tills, and coastal beaches where water action has rounded the originally jagged volcanic rock.
