Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white, gray, or pinkish; Luster: vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: none (fractures across grains); Specific gravity: 2.6-2.7

Formation & Geological History

Formed through the regional or contact metamorphism of quartz-rich sandstone under intense heat and pressure, causing recrystallization of quartz grains. Geological ages vary widely from Precambrian to Cenozoic.

Uses & Applications

Used as crushed stone in road construction, railroad ballast, and as decorative stone in countertops, tiles, and landscaping. Highly valued for its durability and resistance to weathering.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming prominent ridges and hills. It is often confused with marble but is significantly harder.

Field Identification & Locations

Identify in the field by its extreme hardness (cannot be scratched by steel) and the way it fractures through the quartz grains rather than around them. Common in folded mountain belts.

Identified on: 5/3/2026

Mode: Standard