metamorphic

Quartzite

Quartzite (composed primarily of Quartz, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: White to light grey; Luster: Vitreous to dull; Crystal structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific gravity: 2.6-2.7.

Hardness: 7 on Mohs scale
Color: White to light grey
Luster: Vitreous to dull

Identified July 12, 2026More metamorphic →

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Physical properties

Hardness: 7 on Mohs scale; Color: White to light grey; Luster: Vitreous to dull; Crystal structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific gravity: 2.6-2.7.

Formation & geological history

Formed from the metamorphism of quartz sandstone under high heat and pressure, causing the original quartz grains to recrystallize and fuse together. Often found in orogenic belts.

Uses & applications

Used as crushed stone for road construction, railway ballast, and as a decorative stone in architecture and landscaping. High-purity quartzite is used in glass making.

Geological facts

Quartzite is so hard and dense that when a rock hammer hits it, it often produces a spark. Unlike sandstone, when quartzite breaks, it breaks through the quartz grains rather than around them.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Commonly found in mountainous regions or as river-worn cobbles.