metamorphic
Quartzite Pebble
Quartzite
Hardness: 7 (Mohs scale); Color: Grayish-green with white translucent spots; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Grayish-green with white translucent spots
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Grayish-green with white translucent spots; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under extreme heat and pressure, causing the original quartz grains to recrystallize and fuse together. This specimen appears water-worn and rounded by fluvial or glacial transport.
Uses & applications
Used in construction as crushed stone, for road ballast, as a refractory material in glass making, and sometimes polished for decorative purposes or landscaping.
Geological facts
Quartzite is so tough that it often remains as resistant ridges or 'monadnocks' long after softer surrounding rocks have eroded away. It is often confused with marble but will not react with acid.
Field identification & locations
To identify in the field, look for a rock that is harder than glass and has a 'sugary' texture on fresh breaks. This rounded cobble form is common in riverbeds, glacial tills, and along coastal beaches globally.
