igneous
Orbicular/porphyritic stone, likely weathered igneous rock
Indeterminate; possibly orbicular granite or a weathered felsic porphyry
AI-generated identification · may be incorrectPale gray-white, fine- to medium-grained rock with rounded concentric spots and yellow-green weathering; likely quartz–feldspar with mica or chlorite. Estimated Mohs hardness 6–7, vitreous to dull luster, with no obvious cleavage visible; exact texture is obscured by flash and blur.
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Physical properties
Pale gray-white, fine- to medium-grained rock with rounded concentric spots and yellow-green weathering; likely quartz–feldspar with mica or chlorite. Estimated Mohs hardness 6–7, vitreous to dull luster, with no obvious cleavage visible; exact texture is obscured by flash and blur.
Formation & geological history
Likely formed from slowly cooling silica-rich magma, with distinctive orbicules or phenocrysts developing during crystallization, then altered and weathered near the surface. Its geological age cannot be determined from the photograph.
Uses & applications
Decorative stone, lapidary material, and collector specimen; analogous orbicular granites are used for polished slabs and carvings, though this small piece has limited commercial value.
Geological facts
The circular patterns may also represent a fossil, concretion, or mineral-filled vesicle, so a confident identification requires a sharper image and tests such as streak, hardness, acid reaction, and a fresh broken surface.
Field identification & locations
Field clues favor an igneous rock if the circles are embedded crystals with interlocking grains; orbicular granite is known from Finland, Madagascar, Australia, and Corsica. Common rough specimen value is about $5–$30, or $20–$100 if confirmed as attractive orbicular granite.
