metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the original quartz grains to recrystallize and fuse together. Can date from the Precambrian to Cenozoic eras.
Uses & applications
Used as a decorative stone in construction, interior design (countertops), road ballast, and as a source of silica for glassmaking.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock during weathering, forming prominent ridges and hills. It is often confused with marble but can be distinguished by its superior hardness.
Field identification & locations
Identify in the field by its grainy, sugary texture and extreme hardness (it will easily scratch glass). Common in mountainous regions like the Appalachians or the Alps. Collectors look for pieces with interesting iron staining or translucency.
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