Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: White to grey (sometimes pink or reddish); Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing quartz grains to recrystallize and fuse together. Found in orogenic belts and tectonic plate boundaries.

Uses & Applications

Used in construction as crushed stone or decorative facing, in the manufacturing of glass and ceramics, and as railway ballast due to its extreme durability.

Geological Facts

Quartzite is so hard that it can easily scratch steel; in the field, it is distinguished from sandstone because it breaks across quartz grains rather than around them.

Field Identification & Locations

Identify by its grainy, sugary texture and extreme hardness. Commonly found in mountainous regions such as the Appalachian Mountains or the Alps. Look for a conchoidal fracture pattern.

Identified on: 4/29/2026

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