igneous
Red porphyritic volcanic rock, likely rhyolite or andesite
Fine-grained felsic–intermediate volcanic rock; likely quartz/feldspar-bearing rhyolite or andesite
AI-generated identification · may be incorrectDark reddish-purple, dull earthy luster, very fine-grained and massive, with subtle lighter inclusions; hardness roughly 6–7, no obvious cleavage, and moderate density around 2.5–2.7 g/cm³.
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Physical properties
Dark reddish-purple, dull earthy luster, very fine-grained and massive, with subtle lighter inclusions; hardness roughly 6–7, no obvious cleavage, and moderate density around 2.5–2.7 g/cm³.
Formation & geological history
Formed when silica-rich to intermediate lava cooled at or near Earth’s surface; its red color commonly results from oxidation of iron-bearing minerals. Exact age and composition require thin-section or geochemical testing.
Uses & applications
Usually used as decorative stone, landscaping rock, aggregate, or a lapidary specimen; this unpolished piece has little commercial value.
Geological facts
The rounded shape appears naturally water-worn or weathered rather than crystalline. Red volcanic rocks can resemble jasper, but a granular volcanic texture and lack of waxy translucence favor rhyolite or andesite.
Field identification & locations
Common in volcanic terrains worldwide, including the western United States, Mexico, South America, and volcanic island arcs. A hand lens, streak test, density measurement, and acid test can help; thin-section analysis is most reliable.
