metamorphic
Quartzite
Metamorphosed quartz sandstone
AI-generated identification · may be incorrectHardness: 7 on the Mohs scale. Color: Typically shades of pink, purple, red, white, or gray. Luster: Vitreous to greasy. Crystal structure: Trigonal (microcrystalline quartz grains fused together). Cleavage: None, breaks with a conchoidal fracture. Specific gravity: 2.65.
- Hardness
- 7 on the Mohs scale
- Color
- Typically shades of pink, purple, red, white, or gray
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on the Mohs scale. Color: Typically shades of pink, purple, red, white, or gray. Luster: Vitreous to greasy. Crystal structure: Trigonal (microcrystalline quartz grains fused together). Cleavage: None, breaks with a conchoidal fracture. Specific gravity: 2.65.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, typically through tectonic compression in orogenic belts. Geological age varies widely from Precambrian to Cenozoic.
Uses & applications
Used in construction, as crushed stone for road bases, railway ballast, dimension stone, manufacturing silica brick, and occasionally as a decorative gemstone or in countertops.
Geological facts
Unlike sandstone, which breaks around the individual sand grains, quartzite breaks straight through the grains because the quartz cement is exceptionally strong.
Field identification & locations
Identified by its high hardness (scratches glass easily), lack of effervescence with hydrochloric acid, and sugary textured surface where grains are fused together. Found worldwide, especially in mountain ranges.
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