metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: Grayish-white to tan. Luster: Vitreous to dull. Structure: Granoblastic, non-foliated. Cleavage: Indistinct/None. Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white to tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: Grayish-white to tan. Luster: Vitreous to dull. Structure: Granoblastic, non-foliated. Cleavage: Indistinct/None. Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the regional or contact metamorphism of quartz sandstone. Intense heat and pressure cause the original quartz grains to recrystallize and fuse together.
Uses & applications
Used as crushed stone for road construction, railroad ballast, and as a decorative building stone or countertop material.
Geological facts
Quartzite is so tough that it often breaks through the individual quartz grains rather than around them, which distinguishes it from sandstone.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Often found in mountain ranges or ancient shield areas like the Appalachians or the Great Lakes region.
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