Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Pinkish-red (likely due to iron oxide impurities); Luster: Vitreous to greasy; Crystal structure: Trigonal; Cleavage: None, conchoidal fracture; Specific gravity: 2.6-2.7.

Formation & Geological History

Formed through the metamorphism of quartz sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together. Often found in Precambrian or Paleozoic geological environments.

Uses & Applications

Used primarily in construction for crushed stone, road ballast, and decorative stone. Sometimes used in glass making if sufficiently pure, or as gemstones if featuring attractive coloring.

Geological Facts

Quartzite is so tough that it often outlasts the softer surrounding rock, forming prominent ridges and hills. When it breaks, it fractures through the quartz grains, unlike sandstone which breaks around them.

Field Identification & Locations

Identify by its extreme hardness (scratches glass) and sugary texture. Found globally in fold mountain belts. In the field, look for a non-foliated, dense texture that does not fizz with acid.

Identified on: 4/30/2026

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