igneous
Basalt with Quartz/Calcite Vein
Amygdaloidal Basalt (matrix) with Mineral Vein filling
Hardness: 6-7 (basalt matrix), 3 (if calcite vein) or 7 (if quartz vein). Color: Dark grey to charcoal matrix with a white crystallised vein. Luster: Dull/earthy matrix with a vitreous vein. Crystal Structure: Aphanitic (fine-grained) matrix.
- Color
- Dark grey to charcoal matrix with a white crystallised vein
- Luster
- Dull/earthy matrix with a vitreous vein
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Physical properties
Hardness: 6-7 (basalt matrix), 3 (if calcite vein) or 7 (if quartz vein). Color: Dark grey to charcoal matrix with a white crystallised vein. Luster: Dull/earthy matrix with a vitreous vein. Crystal Structure: Aphanitic (fine-grained) matrix.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava. The white vein formed later via hydrothermal activity, where mineral-rich hot water flowed through a crack in the cooling rock and deposited crystals. Common in volcanic terrains across all geological ages.
Uses & applications
Basalt is used extensively as crushed stone for road base, concrete aggregate, and railroad ballast. Small river-worn specimens like this are primarily used for landscaping, decorative gravel, or as pocket stones for collectors.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. The white line is often called a 'Wishing Line' in folklore; it is said that if you find a rock with a continuous line circling it, it will grant a wish.
Field identification & locations
Identify in the field by its high density, dark color, and fine texture. The white vein will not scratch easily if quartz, but will bubble with weak acid (vinegar) if it is calcite. Commonly found on beaches, riverbeds, and volcanic fields.
