metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Pink, white, or orange due to iron oxide impurities; Luster: Vitreous to dull; Crystal structure: Non-foliated, granoblastic; Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Pink, white, or orange due to iron oxide impurities
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Pink, white, or orange due to iron oxide impurities; Luster: Vitreous to dull; Crystal structure: Non-foliated, granoblastic; Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in convergent plate boundaries. This causes the individual sand grains to recrystallize and fuse together.
Uses & applications
Used as a decorative stone in landscaping, as an aggregate in road construction, in the manufacture of glass, and occasionally as a semi-precious gemstone when containing unique colors.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in mountainous areas, forming prominent ridges. It is often confused with marble, but unlike marble, it will not fizz when exposed to acid.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sugary appearance which distinguishes it from massive quartz. Found worldwide in mountainous regions.
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