metamorphic
Quartzite Pebble
Metamorphic Quartzite (primarily SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: grayish-white with light tan and darker gray patches; Luster: vitreous to dull waxy; Cleavage: none, shows conchoidal to sub-conchoidal fracture; Structure: granoblastic interlocking quartz grains.
- Hardness
- 7 on Mohs scale
- Color
- grayish-white with light tan and darker gray patches
- Luster
- vitreous to dull waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: grayish-white with light tan and darker gray patches; Luster: vitreous to dull waxy; Cleavage: none, shows conchoidal to sub-conchoidal fracture; Structure: granoblastic interlocking quartz grains.
Formation & geological history
Formed when pure quartz sandstone undergoes intense heat and pressure during regional or contact metamorphism, recrystallizing the original sand grains into a dense, tightly interlocking mosaic of quartz. Rounded into a pebble through water or glacial tumbling.
Uses & applications
Used widely in construction as crushed stone, railway ballast, and decorative landscaping rock. Exceptionally pure quartzite can be used to manufacture silicon, ferrosilicon, and glass.
Geological facts
Quartzite is so tough and resilient that when broken, it fractures cleanly across the quartz grains rather than along their boundaries, unlike its sedimentary parent rock, sandstone.
Field identification & locations
Can be identified in the field by its extreme hardness (easily scratches glass and steel), lack of reaction with dilute acid, and sugary to vitreous fused granular texture. Common in riverbeds, glacial moraines, and ocean beaches worldwide.
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