metamorphic
Quartzite Pebble
Metamorphic Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, beige, or off-white; Luster: Dull to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoisdal fracture); Specific gravity: 2.63–2.65
- Hardness
- 7 (Mohs scale)
- Color
- Tan, beige, or off-white
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, beige, or off-white; Luster: Dull to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoisdal fracture); Specific gravity: 2.63–2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, usually during mountain-building events. This specific specimen has been further shaped and smoothed by water erosion (river or beach action).
Uses & applications
Used primarily as decorative garden stone, drainage aggregate, and in construction. High-purity quartzite is used in glass making and metallurgy.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the tops of ridges and resistant hills. Unlike sandstone, when quartzite is broken, it fractures through the quartz grains rather than around them.
Field identification & locations
Identify by its hardness (it will scratch glass) and lack of reaction to acid. Look for a sugary texture on fresh breaks. Found globally in ancient riverbeds, beaches, and glaciated plains.
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