metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray; Luster: vitreous (glassy) to dull; Crystal structure: hexagonal/trigonal; Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray
- Luster
- vitreous (glassy) to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray; Luster: vitreous (glassy) to dull; Crystal structure: hexagonal/trigonal; Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together in a dense matrix.
Uses & applications
Used in construction as crushed stone or decorative building stone, in the glass industry as a source of silica, and as a durable material for countertops and flooring.
Geological facts
Quartzite is so tough that it often forms the caprock or ridges of mountain ranges because it resists weathering more effectively than surrounding rocks. It can be distinguished from sandstone because it fractures through the grains rather than around them.
Field identification & locations
Look for a sugary texture that does not scratch with a steel knife. Unlike marble, it will not fizz when exposed to acid. It is commonly found in ancient mountain belts and shields globally.
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