metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with yellow or tan staining; Luster: vitreous to waxy; Structure: granular, non-foliated; Cleavage: none, breaks with a conchoidal or irregular fracture.
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, often with yellow or tan staining
- Luster
- vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often with yellow or tan staining; Luster: vitreous to waxy; Structure: granular, non-foliated; Cleavage: none, breaks with a conchoidal or irregular fracture.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together. Can be found in geological formations ranging from the Proterozoic to more recent eras.
Uses & applications
Used primarily in construction for crushed stone, road ballast, and decorative building stone. High-purity quartzite is also used to produce silica sand for glass making and industrial ceramics.
Geological facts
Quartzite is so durable that it often forms the crests of ridges and mountains because it resists erosion better than the surrounding rocks. It is tougher than sandstone and will break across the quartz grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and its crystalline, sugary appearance. It is commonly found in mountain ranges and metamorphic belts. Collectors look for unique colors or translucent qualities.
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