metamorphic
Quartzite (River Pebbles)
Metamorphosed Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, yellow-orange, honey; Luster: Vitreous to waxy (when wet or polished); Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Tan, yellow-orange, honey
- Luster
- Vitreous to waxy (when wet or polished)
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, yellow-orange, honey; Luster: Vitreous to waxy (when wet or polished); Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events. These specific specimens have been rounded and smoothed by mechanical weathering in a river or coastal environment.
Uses & applications
Used as decorative landscaping stones, aquarium substrate, and in construction as aggregate. High-purity quartzite is used to produce glass and silicon metal.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than around them. It is one of the most durable rocks on the Earth's surface and is often found as 'erratics' far from its source.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its sugary, crystalline texture often visible on fresh breaks. Found globally in ancient mountain belts and river beds draining those areas.
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