metamorphic
Quartzite
Quartzite (Recrystallized Quartz Sandstone)
Hardness: 7 on Mohs scale; Color: White, grey, or tan with dark inclusions; Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz grains; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White, grey, or tan with dark inclusions
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White, grey, or tan with dark inclusions; Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz grains; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together into a dense, non-porous rock.
Uses & applications
Commonly used as crushed stone for road construction, railroad ballast, and as a raw material for glass and ceramics due to high silica content. Attractive pieces are used as decorative garden stones.
Geological facts
Quartzite is so hard that when it breaks, it fractures through the individual sand grains rather than around them. It is one of the most durable rocks on the Earth's surface.
Field identification & locations
Identify in the field by its superior hardness (it will easily scratch glass) and lack of reaction to acid. Look for a sugary texture on fresh breaks. Found globally in mountainous regions and glacial deposits.
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