metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or white with reddish/brown inclusions; Luster: Vitreous to waxy (especially when polished); Crystal Structure: Hexagonal (trigonal); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or white with reddish/brown inclusions
- Luster
- Vitreous to waxy (especially when polished)
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or white with reddish/brown inclusions; Luster: Vitreous to waxy (especially when polished); Crystal Structure: Hexagonal (trigonal); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the quartz grains to recrystallize and fuse together. Often found in orogenic belts and tectonic plate boundaries.
Uses & applications
Used in construction as crushed stone or decorative building facades, for manufacturing glass (if high purity), and as decorative ornaments or river rocks for landscaping.
Geological facts
Quartzite is often harder than the sandstone it originates from and can survive intense weathering, which is why it is often found as smooth cobbles in river beds or on beaches.
Field identification & locations
Identify by its ability to scratch glass and its lack of reaction to acid. It has a sugary texture when broken but feels smooth and dense when polished. Commonly found in areas with ancient mountain ranges.
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