igneous
Basalt with Quartz/Calcite Veining
Aphanitic Mafic Basalt with secondary mineral veining
Hardness: 5-6 (Basalt) / 7 (Quartz veins), Color: dark grey to black with white linear patterns, Luster: dull to earthy, Crystal structure: microcrystalline (aphanitic), Specific gravity: 2.8 - 3.0
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Physical properties
Hardness: 5-6 (Basalt) / 7 (Quartz veins), Color: dark grey to black with white linear patterns, Luster: dull to earthy, Crystal structure: microcrystalline (aphanitic), Specific gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. The white veins are secondary mineral deposits (likely quartz or calcite) that filled fractures in the rock via hydrothermal activity after the basalt had solidified.
Uses & applications
Commonly used as crushed stone for construction, road base, and railroad ballast. Smooth river-worn basalt is often used in landscaping, decorative stone, and massage therapy.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. The white 'veins' seen here create a pattern often referred to by collectors as 'lightning stone' or 'spiderweb basalt' due to the striking contrast.
Field identification & locations
Identified in the field by its dark, fine-grained matrix and heavy feel. Often found in volcanic regions, riverbeds, and coastal beaches where water action has rounded the specimen into a 'cobble' or 'river stone'.
