metamorphic
Tumbled quartz-rich river pebble, possibly quartzite
Quartzite (predominantly SiO₂), or quartz-rich siliceous rock
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; rounded, tan-brown to gray with reddish staining, uneven translucent patches, and a dull to waxy luster. Quartz grains appear tightly fused; cleavage is absent and fracture is irregular to conchoidal. Exact identification is limited by the polished/tumbled surface.
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Physical properties
Hardness about 6.5–7 Mohs; rounded, tan-brown to gray with reddish staining, uneven translucent patches, and a dull to waxy luster. Quartz grains appear tightly fused; cleavage is absent and fracture is irregular to conchoidal. Exact identification is limited by the polished/tumbled surface.
Formation & geological history
Likely formed when quartz-rich sandstone recrystallized during metamorphism, then weathered and rounded by river transport; the rock itself may be Precambrian to younger depending on its source region. Iron-oxide staining and surface weathering produce the brown-red colors.
Uses & applications
Suitable as a decorative pebble, craft material, landscaping stone, or lapidary rough; it has little jewelry value unless it polishes attractively or contains distinctive inclusions.
Geological facts
Quartzite commonly resists weathering better than surrounding rocks, forming ridges and durable stream cobbles. The visible dark patch may be iron/manganese minerals or other inclusions rather than a separate gemstone.
Field identification & locations
A steel file should barely scratch it, while it can scratch ordinary glass; fused granular texture and lack of cleavage support quartzite over softer sandstone. Common in metamorphic belts and river gravels worldwide.
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