metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale), Color: Brownish-tan to reddish due to iron oxide staining, Luster: Vitreous to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: Indistinct, Specific Gravity: 2.63-2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Brownish-tan to reddish due to iron oxide staining, Luster: Vitreous to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: Indistinct, Specific Gravity: 2.63-2.65
Formation & geological history
Formed from the metamorphism of quartz sandstone under extreme heat and pressure, causing the original quartz grains to recrystallize into an interlocking mosaic.
Uses & applications
Used in construction as crushed stone or gravel, in architecture as decorative stone, and occasionally in glassmaking if the silica purity is high.
Geological facts
Quartzite is much harder and more durable than its parent rock, sandstone. Red or brown tints often come from iron impurities like hematite or goethite.
Field identification & locations
Identify by its ability to scratch glass and its grainy, sugary texture. It is commonly found in mountain ranges and glacial deposits.
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