metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, occasionally pink or reddish; Luster: vitreous to dull; Crystal structure: non-clastic, interlocking grains; Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, occasionally pink or reddish
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, occasionally pink or reddish; Luster: vitreous to dull; Crystal structure: non-clastic, interlocking grains; Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically in convergent plate boundaries or orogenic belts. This specimen appears water-worn, likely from a river or beach environment.
Uses & applications
Used in construction as crushed stone, road ballast, and decorative stone. Historically used for stone tools. High-purity quartzite is used to produce glass and silicon metal.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the tops of ridges and mountains because it resists weathering better than the rocks surrounding it.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its sugary texture. Unlike marble, it will not fizz with acid. Common in ancient mountain ranges and glacial deposits.
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