igneous
Weathered quartz-rich pebble
Likely quartz-bearing granite or granitic gneiss; exact identification requires testing
AI-generated identification · may be incorrectHardness approximately 6–7 Mohs; tan-brown, fine-to-medium granular texture, dull to weakly vitreous luster, and no obvious cleavage. Rounded shape and surface staining indicate abrasion and weathering; visible grains may include quartz, feldspar, and mica.
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Physical properties
Hardness approximately 6–7 Mohs; tan-brown, fine-to-medium granular texture, dull to weakly vitreous luster, and no obvious cleavage. Rounded shape and surface staining indicate abrasion and weathering; visible grains may include quartz, feldspar, and mica.
Formation & geological history
Probably a naturally weathered stream or beach pebble derived from an older continental igneous or metamorphic source, commonly Precambrian to Paleozoic in age. Iron-oxide staining produces the brown coloration.
Uses & applications
As an individual specimen it has little commercial value; similar granite is widely used as crushed stone, aggregate, building stone, and countertops. It is not gem-quality based on the image.
Geological facts
Quartz-rich rocks commonly leave a scratch on glass, while feldspar-rich portions are softer. The rounded exterior reflects transport by water, ice, or sediment movement.
Field identification & locations
Look for interlocking quartz and feldspar grains, occasional dark mica, and a scratch hardness near quartz; a streak, acid test, and fresh broken surface would improve identification. Common worldwide in riverbeds, glacial deposits, and eroded uplands.
