metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs); Color: Grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6-2.7. It is extremely durable and scratch-resistant.
- Hardness
- 7 (Mohs)
- Color
- Grayish-white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs); Color: Grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6-2.7. It is extremely durable and scratch-resistant.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure causes quartz grains to recrystallize and fuse together into a dense, hard rock. This specimen shows significant rounding due to fluvial (river) or beach erosion.
Uses & applications
Commonly used as crushed stone in road construction, as railroad ballast, or in landscaping. Because of its hardness, it is also used as a raw material for ceramics and glass manufacturing.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, remaining as rugged ridges or resistant pebbles after other materials have eroded away.
Field identification & locations
Identify by its ability to scratch glass easily and its lack of reaction to acid. In the field, look for a sugary or grainy appearance on fresh breaks. It is found globally, particularly in ancient mountain belts.
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