metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white to tan; Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz grains; Cleavage: None (conchoidal fracture); 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; Crystal structure: Non-foliated, interlocking quartz grains; Cleavage: None (conchoidal fracture); 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 (orogenic belts) across various geological eras.
Uses & applications
Used in construction as road ballast, roofing granules, and decorative stone; also used in the glass and silicate industry due to high silica content.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in the landscape, forming prominent ridges and peaks. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its sugary texture on fresh breaks and its inability to be scratched by a steel knife. It is commonly found in riverbeds as rounded cobbles or in massive outcrops in metamorphic terrains.
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