metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Gray, tan, or yellowish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None, fractures conchoidally; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Gray, tan, or yellowish-white
- Luster
- Vitreous to dull
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale; Color: Gray, tan, or yellowish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None, fractures conchoidally; Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together, creating a dense, interlocking matrix.
Uses & applications
Used extensively as decorative stone in architecture, as crushed stone for road construction and railway ballast, and occasionally in glassmaking if pure enough.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock, forming prominent ridges and peaks in mountain ranges. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify by its sugary texture and extreme hardness; unlike sandstone, quartzite breaks through the quartz grains rather than around them. Found globally in ancient mountain belts and Precambrian shields.
More like this
