igneous
Basalt with Quartz Vein
Basalt (extrusive igneous rock) with Quartz (SiO2) inclusion
Hardness: 6-7 (Mohs scale), Color: Dark grey to black matrix with white/cream vein, Luster: Dull/earthy (matrix) to vitreous (vein), Structure: Fine-grained/aphanitic, Cleavage: None
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Dark grey to black matrix with white/cream vein, Luster: Dull/earthy (matrix) to vitreous (vein), Structure: Fine-grained/aphanitic, Cleavage: None
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the earth's surface. The vein formed later through hydrothermal activity where mineral-rich water filled cracks in the rock. Typically found in volcanic regions and ocean floors.
Uses & applications
Usually used for construction aggregate, road base, and landscape decoration. Polished river stones of this type are popular in meditation gardens and aquariums.
Geological facts
This specimen is a water-worn river pebble. The smooth, rounded shape indicates it has been transported long distances by water, causing mechanical weathering that smoothed its edges.
Field identification & locations
Identify by its heavy weight, dark fine-grained appearance, and the presence of a distinct protruding mineral line (vein). Commonly found on beaches or in riverbeds in volcanic geographies.
