igneous
Rhyolite with Black Tourmaline
Extrusive felsic igneous rock with schorl inclusions
AI-generated identification · may be incorrectHardness of 6-7 on Mohs scale, earthy pinkish-brown groundmass with distinct black tabular tourmaline crystals, dull to subvitreous luster, aphanitic texture.
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Physical properties
Hardness of 6-7 on Mohs scale, earthy pinkish-brown groundmass with distinct black tabular tourmaline crystals, dull to subvitreous luster, aphanitic texture.
Formation & geological history
Formed from rapid cooling of silica-rich lava at Earth's surface, often associated with volcanic domes and flows.
Uses & applications
Used primarily as decorative lapidary material, ornamental stone, and by mineral collectors.
Geological facts
The black spots are tourmaline crystals that grew in cavities or as phenocrysts during late-stage magmatic cooling.
Field identification & locations
Identify by its fine-grained felsic matrix dotted with contrasting prismatic black crystals; found in volcanic regions worldwide.
