metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan; Luster: Vitreous to dull; Crystal structure: Trigonal (granular); Cleavage: None (conchoidal fracture); 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: Trigonal (granular); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events (orogeny). The original sand grains recrystallize into an interlocking mosaic.
Uses & applications
Used as a decorative stone in architecture, as crushed stone for road construction, in the manufacture of glass and ceramics, and as a durable material for kitchen countertops.
Geological facts
Quartzite is so hard that it will scratch glass and steel. It is frequently confused with white marble, but unlike marble, it will not react with acid or be easily scratched by a knife.
Field identification & locations
Identify in the field by its extreme hardness and granular, sugary appearance on freshly broken surfaces. It is resistant to chemical weathering and often forms prominent ridges or hills.
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