metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan; Luster: vitreous to dull; Crystal structure: hexagonal (trigonal); Cleavage: none; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or tan
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan; Luster: vitreous to dull; Crystal structure: hexagonal (trigonal); Cleavage: none; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events (orogeny). Primarily Paleozoic to Precambrian in age.
Uses & applications
Used in construction as crushed stone for road gravel, as decorative building stone, and historically as a tool stone for making sharp edges (projectile points).
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges it forms, creating prominent ridges or peaks. It is frequently mistaken for marble but can be distinguished because it can scratch glass.
Field identification & locations
Identify in the field by its granular, sugary texture and extreme hardness. Often found in folded mountain belts like the Appalachians or the Alps. It breaks through the quartz grains rather than around them.
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