metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Gray, white, or reddish due to iron impurities; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Gray, white, or reddish due to iron impurities
- 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, white, or reddish due to iron impurities; 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 quartzose sandstone. Intense heat and pressure cause the quartz grains to recrystallize and fuse together, creating a dense, hard rock. This specimen appears weathered, likely found in a glacial or fluvial environment.
Uses & applications
Used as crushed stone for road construction, railway ballast, and in the production of glass and industrial silica. High-quality slabs are used for countertops and flooring.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than along their boundaries, unlike the sandstone from which it originated. It is one of the most durable rocks on Earth's surface.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sugary appearance. It often creates prominent ridges in mountain ranges due to its resistance to erosion. Found globally in ancient mountain belts.
More like this
