metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically grey, white, or tan with a sugary texture; Luster: Vitreous to dull; Crystal structure: Trigonal/hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 to 2.7.
- Hardness
- 7 on Mohs scale
- Color
- typically grey, white, or tan with a sugary texture
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically grey, white, or tan with a sugary texture; Luster: Vitreous to dull; Crystal structure: Trigonal/hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 to 2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, creating an extremely durable rock. Primarily found in mountain belts and Precambrian terrains.
Uses & applications
Used widely in construction as crushed stone for road bases and railway ballast. Due to its durability, it is also used for countertops, wall cladding, and decorative landscaping stones.
Geological facts
Quartzite is so hard that it can scratch steel and glass. Unlike sandstone, which breaks between grains, quartzite breaks through the quartz grains because the rock is so tightly fused.
Field identification & locations
Identify in the field by its hardness and granular, sparkling texture on fresh breaks. It is often found in mountainous regions or as rounded cobbles in riverbeds. Collectors look for unique colors or bands within the specimen.
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