igneous
Quartz-veined Basalt
Basalt with Quartz Infill (SiO2 + Fe/Mg Silicates)
Hardness: 6-7 (Mohs); Color: Dark grey to black matrix with white crystalline veins; Luster: Dull/earthy (matrix) to vitreous (vein); Texture: Fine-grained aphanitic with macro-crystalline veins.
- Hardness
- 6-7 (Mohs)
- Color
- Dark grey to black matrix with white crystalline veins
- Luster
- Dull/earthy (matrix) to vitreous (vein)
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Physical properties
Hardness: 6-7 (Mohs); Color: Dark grey to black matrix with white crystalline veins; Luster: Dull/earthy (matrix) to vitreous (vein); Texture: Fine-grained aphanitic with macro-crystalline veins.
Formation & geological history
Formed through rapid cooling of mafic lava (basalt) followed by hydrothermal activity where silica-rich fluids filled fractures or vesicles (gas bubbles) to form quartz crystalline growth. These can range from hundreds of thousands to millions of years old.
Uses & applications
Primarily used as a decorative river stone, in landscaping, or as a pocket stone for collectors. Basalt itself is widely used in road construction and as aggregate.
Geological facts
The white patterns are often referred to as 'lightning strikes' or 'starbursts' by beachcombers. They are common in volcanic regions where tectonic activity creates cracks in cooled lava.
Field identification & locations
Identify in the field by the high contrast between the dark, heavy volcanic base and the hard, translucent white quartz. Commonly found on volcanic coastlines or in glacial till.
