metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: White, gray, or tan with iron-oxide staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline/interlocking); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 7 (Mohs scale)
- Color
- White, gray, or tan with iron-oxide staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: White, gray, or tan with iron-oxide staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline/interlocking); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional or contact metamorphism of quartzose sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. It can date from almost any geological age where tectonic activity has occurred.
Uses & applications
Used primarily in construction for crushed stone, road ballast, and railway ballast. Due to its resistance to weathering and hardness, it is also used as a decorative building stone, for kitchen countertops, and as a source of silica in glass manufacturing.
Geological facts
Quartzite is so hard that it will scratch glass and steel. In the stone industry, it is often confused with marble or granite, but it is much more durable than marble and lacks the feldspar content of granite.
Field identification & locations
Identify in the field by its granular, sugary texture and extreme hardness. Unlike limestone, it will not fizz with acid. It is commonly found in mountain ranges and folded belts where sedimentary layers have been buried and squeezed.
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