metamorphic
Quartzite Pebble (River-worn Quartzite / Vein Quartz)
Quartzite (predominantly SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: light grayish-white to milky with pale brownish-yellow patches; Luster: vitreous to waxy/dull when unpolished; Fracture: conchoidal to uneven; Specific Gravity: ~2.65; Structure: interlocking crystalline granular texture.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to waxy/dull when unpolished
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Physical properties
Hardness: 7 on Mohs scale; Color: light grayish-white to milky with pale brownish-yellow patches; Luster: vitreous to waxy/dull when unpolished; Fracture: conchoidal to uneven; Specific Gravity: ~2.65; Structure: interlocking crystalline granular texture.
Formation & geological history
Formed from quartz-rich sandstone subjected to regional or contact metamorphism under high heat and pressure, causing quartz grains to recrystallize into a dense, fused network. Subsequently eroded, transported by water or glacial action, and naturally tumbled into a smooth river pebble.
Uses & applications
Commonly used in crushed form as railroad ballast, aggregate in construction, manufacturing of refractory bricks, landscape gardening, and tumbling/lapidary craft.
Geological facts
Quartzite is so tough and chemically resistant that it frequently forms prominent ridges and peaks in mountainous terrain. Unlike sandstone, when quartzite breaks, the fractures cut across the individual quartz grains rather than along their boundaries.
Field identification & locations
Recognized in the field by its extreme hardness (scratches glass easily, cannot be scratched with a standard steel knife blade), sub-translucent crystalline sugary appearance, and rounded river-tumbled shape. Abundant globally in riverbeds, beaches, and glacial deposits.
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