metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: tan, reddish-brown, or translucent peach; Luster: dull to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: none, conchoidal fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- tan, reddish-brown, or translucent peach
- Luster
- dull to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: tan, reddish-brown, or translucent peach; Luster: dull to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: none, conchoidal fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under heat and pressure. This specimen shows significant rounding and frosting, indicating it was subsequently transported and eroded by water in a high-energy environment like a river or beach.
Uses & applications
Used as industrial abrasive, aggregate in construction, decorative landscaping stones, and sometimes as 'tumbled stones' for beginner collectors.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than around them, unlike sandstone. It is one of the most durable rocks on the Earth's surface.
Field identification & locations
Identify by its hardness (it will easily scratch glass) and its sugary texture under a magnifying lens. Commonly found in glacial till, river beds, and coastal areas throughout North America and Europe.
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