igneous
Banded rhyolite (likely flow-banded volcanic rock)
Rhyolite, composed mainly of quartz, alkali feldspar, and plagioclase with volcanic glass and iron-oxide alteration
AI-generated identification · may be incorrectFine-grained, pink-gray, and weakly lustrous with wavy flow banding and scattered dark inclusions. Typical hardness is about 6–7 Mohs; cleavage is absent or indistinct and specific gravity is roughly 2.4–2.7.
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Physical properties
Fine-grained, pink-gray, and weakly lustrous with wavy flow banding and scattered dark inclusions. Typical hardness is about 6–7 Mohs; cleavage is absent or indistinct and specific gravity is roughly 2.4–2.7.
Formation & geological history
Formed when silica-rich lava cooled rapidly near Earth’s surface, preserving streaks of different magma compositions and textures. Such rocks commonly range from Cenozoic to Precambrian in age, depending on locality.
Uses & applications
Used locally as decorative stone, aggregate, and landscaping material; attractive pieces may be collected or polished, but this specimen has modest commercial value.
Geological facts
Flow banding records movement and stretching of viscous rhyolitic lava. The pink coloration commonly reflects potassium feldspar and iron staining.
Field identification & locations
Look for pale pink, gray, or cream fine-grained material with curved or parallel bands, unlike coarse granite. Common in volcanic belts and caldera regions, including the western United States, Mexico, and New Zealand.
