metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness 7 (Mohs scale); Color: off-white with tan and rust staining; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); specific gravity: 2.6-2.7.
- Color
- off-white with tan and rust staining
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness 7 (Mohs scale); Color: off-white with tan and rust staining; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional metamorphism of quartz sandstone. The original quartz sand grains are recrystallized under high heat and pressure, interlocking to form a very hard, durable rock.
Uses & applications
Used in construction as crushed stone or decorative landscaping. Large deposits are used as high-purity silica for glassmaking and industrial abrasives.
Geological facts
Unlike sandstone, which breaks around the sand grains, quartzite is so well-fused that it breaks through the grains when fractured.
Field identification & locations
Identify by its hardness (scratches glass) and smoother, sugary texture compared to sandstone. It is ubiquitous in riverbeds and mountainous terrain worldwide.
