Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white to gray; Luster: vitreous (glassy) to dull; Crystal structure: Hexagonal (individual grains); Cleavage: none, breaks with conchoidal or irregular fracture.

Formation & Geological History

Formed through the regional metamorphism of quartz sandstone. Intense heat and pressure cause the individual sand grains to recrystallize and fuse together. It can be found in mountain ranges and areas with ancient tectonic activity.

Uses & Applications

Used as a decorative stone in architecture, as crushed stone for road construction and railroad ballast, in the production of glass and silicon, and occasionally as a gemstone in primitive jewelry.

Geological Facts

Quartzite is so strong that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike sandstone which usually breaks between grains.

Field Identification & Locations

Identify by its extreme hardness (it will easily scratch glass or steel) and sugary, crystalline appearance. It is commonly found in erosion-resistant ridges. Collectors should look for unique color variations caused by trace mineral impurities.

Identified on: 4/15/2026

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