Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Grayish-white with some pink/beige tones; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65.

Formation & Geological History

Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. The geological age varies depending on the original sandstone deposit, ranging from Proterozoic to more recent orogenic belts.

Uses & Applications

Used as crushed stone for road construction, railway ballast, and as a decorative stone in architecture and landscaping. In industry, high-purity quartzite is used to produce silica sand and silicon metal.

Geological Facts

Quartzite is so hard and chemically resistant that it often forms prominent ridges and hilltops because it weathers much more slowly than surrounding rocks. It is harder than steel and will easily scratch glass.

Field Identification & Locations

Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sandpaper-like texture that does not rub off. It is commonly found in mountainous regions or glacial till. Collectors look for pieces with unique colors or translucency.

Identified on: 4/27/2026

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