metamorphic

Quartz-rich rock, likely milky quartz or quartzite

Quartz (SiO₂); possibly quartzite, a metamorphosed quartz sandstone

AI-generated identification · may be incorrect

Hardness about 7 Mohs; white to gray with rusty iron-oxide staining, vitreous to dull luster, massive granular texture, and no obvious cleavage. The specimen appears dense and opaque-to-translucent at thin edges.

Identified September 15, 2026More metamorphic →

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Physical properties

Formation & geological history

If quartzite, it formed when quartz-rich sandstone recrystallized under heat and pressure, commonly during Precambrian to Paleozoic mountain-building. If a quartz vein fragment, it crystallized from silica-rich hydrothermal fluids in fractures.

Uses & applications

Quartzite is used as crushed stone, road aggregate, building stone, and occasionally decorative material; attractive milky quartz is collected but generally has modest gem value.

Geological facts

Quartz is one of Earth’s most abundant minerals and is highly resistant to weathering, allowing quartz-rich pebbles and boulders to persist in soils and streambeds.

Field identification & locations

Look for glassy quartz grains fused into a hard mass, no acid reaction, and ability to scratch ordinary glass; a steel knife should not scratch it. Common in mountain belts, river gravels, and quartz veins worldwide.