metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan to off-white; Luster: Vitreous to dull when weathered; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan to off-white
- Luster
- Vitreous to dull when weathered
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to off-white; Luster: Vitreous to dull when weathered; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.65
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. Through intense heating and pressure, usually related to tectonic compression in orogenic belts, the original quartz grains recrystallize and fuse together.
Uses & applications
Commonly used as decorative gravel, in construction as crushed stone for road ballast, or as a source of silica for glass manufacturing.
Geological facts
Quartzite is so tough that it often survives intense weathering that destroys other rocks, which is why it is frequently found as rounded pebbles in riverbeds and on beaches.
Field identification & locations
Identify in the field by its hardness (it will scratch glass easily) and its granular, sugary texture. Unlike sandstone, quartzite breaks across the grains rather than around them. Found globally in mountainous regions.
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