metamorphic
Quartzite
Quartzite (primarily SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale); Color: Gray, white, or brown with a glassy appearance; Luster: Vitreous to dull; Crystal structure: Trigonal (as quartz grains); Cleavage: None; Specific gravity: 2.6 - 2.7.
- Hardness
- 7 (Mohs scale)
- Color
- Gray, white, or brown with a glassy appearance
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Gray, white, or brown with a glassy appearance; Luster: Vitreous to dull; Crystal structure: Trigonal (as quartz grains); Cleavage: None; Specific gravity: 2.6 - 2.7.
Formation & geological history
Formed through the metamorphism of quartz sandstone by intense heat and pressure, typically during mountain-building events. The original quartz grains recrystallize into a dense, interlocking mosaic.
Uses & applications
Used in construction as crushed stone for road grit and railway ballast. Due to its durability, it is also used for floor tiles, countertops, and as a raw material for glass and silicone production.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caprock or ridges of mountain ranges because it resists weathering better than surrounding rocks.
Field identification & locations
Identify by its ability to scratch glass and its granular, sugary texture that, unlike sandstone, breaks through the grains rather than around them. Found globally in ancient mountain belts.
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