igneous
Basalt with Quartz Veins
Mafic Igneous Rock (primarily Plagioclase and Pyroxene) with SiO2 inclusions
Hardness: 6-7 Mohs; Color: Dark grey to black matrix with white/yellowish linear veins; Luster: Dull to sub-metallic; Structure: Fine-grained aphanitic matrix; Cleavage: None (conchoidal fracture)
- Hardness
- 6-7 Mohs
- Color
- Dark grey to black matrix with white/yellowish linear veins
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: Dark grey to black matrix with white/yellowish linear veins; Luster: Dull to sub-metallic; 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 or near the Earth's surface. The veins were formed later when silica-rich hydrothermal fluids filled fractures in the cooling rock.
Uses & applications
Primarily used as decorative river stones, landscaping, or as an aggregate in construction. High-quality smooth specimens are used in 'worry stones' or meditation sets.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. The white stripes are evidence of ancient seismic or tectonic activity that cracked the rock, allowing mineral-rich water to seep in.
Field identification & locations
Identify in the field by its dark, heavy feel and characteristic 'stripe' crossing the body of the stone. Commonly found in riverbeds, glacial tills, and coastal areas.
