igneous
Basalt with Quartz/Calcite Veins
Aphanitic Mafic Igneous Rock (Hydrothermal Veined)
Hardness: 6-6.5 (matrix) and 7 (veins); Color: Dark grey to black matrix with white/off-white banding; Luster: Dull/earthy for matrix, vitreous for veins; Crystal structure: Aphanitic (fine-grained); Cleavage: None/irregular.
- Hardness
- 6-6
- Color
- Dark grey to black matrix with white/off-white banding
- Luster
- Dull/earthy for matrix, vitreous for veins
Identified More igneous →
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Physical properties
Hardness: 6-6.5 (matrix) and 7 (veins); Color: Dark grey to black matrix with white/off-white banding; Luster: Dull/earthy for matrix, vitreous for veins; Crystal structure: Aphanitic (fine-grained); Cleavage: None/irregular.
Formation & geological history
Formed from rapid cooling of magnesium-rich and iron-rich lava. The white bands represent secondary mineral precipitation (quartz or calcite) in former fractures via hydrothermal fluids. These occur in volcanic fields and oceanic crust.
Uses & applications
Basalt is used heavily in construction (as aggregate), road building, and for industrial pavers. Veined specimens like this are primarily of interest to hobbyist collectors and used in decorative landscaping.
Geological facts
Basalt is the most common rock type in Earth's crust, making up most of the ocean floor. The white stripes are evidence of 'healing' where the rock cracked under pressure and minerals crystallized in the gap.
Field identification & locations
Identified by its heavy weight, dark fine-grained appearance, and prominent contrasting mineral veins. Commonly found on beaches, riverbeds, and near volcanic outcrops.
