metamorphic
Quartzite (River Pebble)
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, orange, honey, or creamy white; Luster: Vitreous to waxy when wet; Structure: Granular, crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.63-2.65
- Hardness
- 7 (Mohs scale)
- Color
- Tan, orange, honey, or creamy white
- Luster
- Vitreous to waxy when wet
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, orange, honey, or creamy white; Luster: Vitreous to waxy when wet; Structure: Granular, crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.63-2.65
Formation & geological history
Formed when quartz-rich sandstone is subjected to intense heat and pressure (metamorphism), causing the individual quartz grains to recrystallize into a dense, interlocking mosaic of crystals. This specimen has been further shaped and smoothed by fluvial or coastal erosion.
Uses & applications
Industrial use in glassmaking, construction aggregate, decorative landscaping, and occasional use in jewelry as 'sea glass' style pendants. High durability makes it common for abrasives.
Geological facts
Quartzite is so strong that it will typically break through the quartz grains rather than around them. It is one of the most weather-resistant rocks on the Earth's surface.
Field identification & locations
Identify by its hardness (will scratch glass) and lack of reaction to acid. Often found in riverbeds, beaches, and glacial till. Field identification involves looking for a sugary texture on fresh breaks and a lack of layers.
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