metamorphic

Likely polished gray quartzite or chert

Quartzite, predominantly microcrystalline SiO₂; possibly gray chert (chalcedony/quartz)

AI-generated identification · may be incorrect

Smooth, rounded, gray-brown specimen with subdued waxy to vitreous luster and pale vein-like markings. Likely hardness about 6.5–7 Mohs, no obvious cleavage, and specific gravity around 2.6; the image does not resolve grain size well enough for certainty.

Identified September 13, 2026More metamorphic →

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Physical properties

Formation & geological history

If quartzite, it formed when quartz-rich sandstone was recrystallized during metamorphism, commonly in Precambrian to younger mountain belts. If chert, it formed by silica precipitation or replacement in sedimentary environments. Both are plausible around the San Bernardino region.

Uses & applications

Commonly used as aggregate, riprap, paving, and decorative stone; attractive polished pieces are used for lapidary objects and cabochons. This individual appears more like a field or worksite specimen than gem material.

Geological facts

The regular pale lines may be fractures, quartz veins, or saw/polishing marks rather than natural banding. Quartz-rich rocks can scratch ordinary glass but should not scratch corundum or diamond.

Field identification & locations

Around 34.1°N, 117.6°W, quartz-rich metamorphic and sedimentary cobbles are plausible, though local provenance cannot be confirmed visually. Test hardness and inspect a fresh surface: interlocking granular quartz favors quartzite; smooth, uniformly microcrystalline texture favors chert.