metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or off-white with yellow/orange iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or off-white with yellow/orange iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or off-white with yellow/orange iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure. This specimen appears water-worn, likely from a river or glacial deposit, polishing the surface over thousands of years.
Uses & applications
Used in construction as road ballast, railway ballast, and decorative stone. Highly pure quartzite is used to produce glass and industrial silicon.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock layers, forming spectacular ridges and mountain peaks. It is one of the most durable rocks on Earth's surface.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its grainy, sandpaper-like texture beneath a smooth weathered surface. Often found in riverbeds or mountain outcroppings.
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