metamorphic

Quartzite

Quartzite (primarily SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs); Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Granular texture.

Hardness: 7 (Mohs)
Color: White to light gray
Luster: Vitreous to dull

Identified July 15, 2026More metamorphic →

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Physical properties

Hardness: 7 (Mohs); Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Granular texture.

Formation & geological history

Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny). Most quartzite dates back to the Proterozoic or Paleozoic eras.

Uses & applications

Used in construction as crushed stone, road ballast, or dimensional stone for floor tiles/counters. High-purity quartzite is used in glass making and metallurgy.

Geological facts

Quartzite is so hard and resistant that it often forms prominent ridges and hills while surrounding softer rocks erode away. It is often confused with marble, but quartzite will scratch glass while marble will not.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel blade) and its sugary, granular appearance. Commonly found in metamorphic belts worldwide, such as the Appalachian Mountains.