igneous
Basalt with Jasper Vein
Extrusive Igneous Rock with Quartz/Chalcedony Vein
Hardness: 6-7 on Mohs scale (for the vein), 5-6 (for the basalt matrix); Color: Dark grey to black with a prominent reddish-orange vein; Luster: Dull to sub-vitreous; Crystal structure: Microcrystalline to cryptocrystalline
- Color
- Dark grey to black with a prominent reddish-orange vein
- Luster
- Dull to sub-vitreous
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale (for the vein), 5-6 (for the basalt matrix); Color: Dark grey to black with a prominent reddish-orange vein; Luster: Dull to sub-vitreous; Crystal structure: Microcrystalline to cryptocrystalline
Formation & geological history
Formed from the rapid cooling of basaltic lava flows at the Earth's surface, later fractured, with hydrothermal fluids depositing silica (jasper) into the fissure.
Uses & applications
Used primarily as a geological specimen, in lapidary work, and sometimes as crushed stone in construction.
Geological facts
Veins in volcanic rocks like this form when silica-rich mineral solutions precipitate inside cracks deep underground or near the surface long after the initial rock has cooled.
Field identification & locations
Easily identified in the field by its dark, fine-grained volcanic matrix contrasting sharply with a distinct mineral vein running through it.
