metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: light gray to tan; Luster: dull to vitreous; Crystal structure: hexagonal (granular microcrystalline); Cleavage: none; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- light gray to tan
- Luster
- dull to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: light gray to tan; Luster: dull to vitreous; Crystal structure: hexagonal (granular microcrystalline); Cleavage: none; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure from tectonic activity cause the quartz grains to recrystallize and fuse together.
Uses & applications
Used as a common construction aggregate, in road metal, as decorative landscaping stone, and historically as a material for stone tools due to its hardness.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock layers, forming prominent ridges or rounded river pebbles like this one. It is harder than steel and can scratch glass easily.
Field identification & locations
Identify by its extreme hardness and granular, sugary texture. It is commonly found in riverbeds, glacial deposits, and mountain ranges where ancient sea beds have been uplifted.
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