metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan; Luster: vitreous (glassy) to waxy; Structure: non-foliated, interlocking quartz crystals; Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or tan
- Luster
- vitreous (glassy) to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan; Luster: vitreous (glassy) to waxy; Structure: non-foliated, interlocking quartz crystals; 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, losing their original sedimentary texture.
Uses & applications
Used extensively in the construction industry as crushed stone for road bases and railway ballast. High-purity quartzite is used to produce ferrosilicon and industrial sand. It is also used as decorative building stone and in jewelry.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock during weathering, forming prominent ridges and hills. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its hardness and sugary, crystalline appearance. Unlike sandstone, when quartzited is broken, the fracture goes through the quartz grains rather than around them. Found globally in ancient mountain belts and river beds.
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