igneous
Basalt with Quartz Vein
Basalt (Mafic volcanic rock) with secondary Quartz (SiO2) intrusion
Hardness: 6 (basalt) to 7 (quartz); Color: Matte black/dark grey host rock with a translucent white/cream vein; Luster: Dull to sub-vitreous; Structure: Fine-grained/aphanitic matrix with a linear crystalline vein.
- Hardness
- 6 (basalt) to 7 (quartz)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6 (basalt) to 7 (quartz); Color: Matte black/dark grey host rock with a translucent white/cream vein; Luster: Dull to sub-vitreous; Structure: Fine-grained/aphanitic matrix with a linear crystalline vein.
Formation & geological history
Basalt forms from the rapid cooling of magnesium-rich and iron-rich lava at the surface. The white line is a vein formed later when hydrothermal fluids (hot water) rich in silica filled a fracture in the basalt and crystallized into quartz.
Uses & applications
Basalt is used extensively in construction as crushed stone for roads and concrete. Veined specimens like this are primarily collected for hobbyist interest or used as decorative garden stones.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. The presence of a single, clean vein like the one shown is often referred to by collectors as a 'wishing stone' in folklore.
Field identification & locations
Identify in the field by its dark, heavy, fine-grained mass and the distinct color contrast of the vein. Common in volcanic regions, riverbeds, and coastal areas.
