igneous
Quartz-bearing volcanic rock, likely vesicular basalt
Basalt with secondary quartz (SiO₂) and possible zeolite/chalcedony infill
AI-generated identification · may be incorrectDark gray-brown, fine-grained, dull to slightly glassy matrix with a cavity containing pale translucent crystals. Basalt hardness is about 5–6 Mohs; quartz is 7, with no obvious cleavage and a typical quartz luster.
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Physical properties
Dark gray-brown, fine-grained, dull to slightly glassy matrix with a cavity containing pale translucent crystals. Basalt hardness is about 5–6 Mohs; quartz is 7, with no obvious cleavage and a typical quartz luster.
Formation & geological history
Likely formed from rapidly cooled mafic lava, probably Cenozoic or younger, with later groundwater depositing quartz or zeolite crystals in vesicles. Exact age and identity require a fresh surface, hardness testing, and mineral analysis.
Uses & applications
Primarily a field or collector specimen; basalt is widely used as aggregate, roadstone, and building material, while quartz crystals have minor ornamental value.
Geological facts
The rounded cavity is a vesicle formed by escaping volcanic gases; its mineral lining is called an amygdule. The pale crystals may alternatively be calcite or zeolite rather than quartz.
Field identification & locations
Look for a dark fine-grained volcanic matrix, vesicles, high density, and crystals lining cavities; quartz scratches glass, whereas calcite fizzes in dilute acid. Common in basaltic lava flows worldwide, especially volcanic terrains.
