metamorphic
Quartzite Pebble
Si02 (Metamorphosed Sandstone)
Hardness: 7 (Mohs scale); Color: light grey to tan with faint banding; Luster: vitreous to dull; Crystal structure: granular/monocrystalline; Cleavage: none; Specific gravity: approx. 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- light grey to tan with faint banding
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: light grey to tan with faint banding; Luster: vitreous to dull; Crystal structure: granular/monocrystalline; Cleavage: none; Specific gravity: approx. 2.65.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, causing quartz grains to recrystallize and fuse together. Typically Precambrian to Paleozoic in age.
Uses & applications
Used as decorative gravel, in construction as crushed stone, and sometimes as a source of high-purity silica for glassmaking or silicon metal production.
Geological facts
Quartzite is extremely durable and weather-resistant. In many places, quartzite ridges remain as high points in the landscape because the surrounding softer rock has eroded away.
Field identification & locations
Identified in the field by its inability to be scratched by a steel knife and its grainy, sugary appearance on fresh breaks. Very common in riverbeds and glacial deposits.
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