metamorphic

Quartzite pebble

Quartzite (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale. Color: Often white, gray, yellowish, or brownish due to iron oxide impurities (as seen here). Luster: Vitreous to greasy. Crystal structure: Granular, interlocking quartz crystals. No cleavage. Specific gravity: 2.6-2.8.

Hardness: 7 on Mohs scale
Luster: Vitreous to greasy

Identified September 19, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when quartz-rich sandstone is subjected to high heat and pressure, causing the sand grains and silica cement to recrystallize into an interlocking mosaic of quartz crystals. Found in metamorphic terrains worldwide.

Uses & applications

Used in construction as decorative stone, crushed stone for road bases, and sometimes for countertops. Also tumbled and polished for collecting.

Geological facts

Because it is so hard and resistant to weathering, quartzite often forms prominent ridges and peaks in mountainous areas.

Field identification & locations

Identified by its hardness (scratches glass), granular texture (though heavily smoothed here by water action), and lack of fizzing with acid. Common in riverbeds and glacial deposits where it has been rounded into pebbles.