igneous
Basalt with Quartz Vein
Aphanitic Mafic Igneous Rock with Silicon Dioxide (SiO2) inclusion
Hardness: 6-7 (Mohs); Color: Dark grey to charcoal matrix with a white/cream band; Luster: Dull/Earthly matrix with vitreous vein; Structure: Microcrystalline (aphanitic) matrix; Specific Gravity: 2.8–3.0
- Hardness
- 6-7 (Mohs)
- Color
- Dark grey to charcoal matrix with a white/cream band
- Luster
- Dull/Earthly matrix with vitreous vein
Identified More igneous →
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Physical properties
Hardness: 6-7 (Mohs); Color: Dark grey to charcoal matrix with a white/cream band; Luster: Dull/Earthly matrix with vitreous vein; Structure: Microcrystalline (aphanitic) matrix; Specific Gravity: 2.8–3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava. The white stripe is a hydrothermal vein formed when mineral-rich hot water filled a crack in the rock and crystallized into quartz over time.
Uses & applications
Commonly used as aggregate in construction, road base, and concrete. Smooth river-worn specimens are popular for garden landscaping and decorative 'wishing stones'.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. When a single continuous vein circles the entire stone, it is folklorically known as a 'Wishing Stone'.
Field identification & locations
Identify by its heavy weight relative to size and dark, fine-grained texture. Look for the distinct color contrast of the mineral vein. Found worldwide in volcanic regions or as rounded cobbles in riverbeds and beaches.
