Quartzite

Physical Properties

Hardness: 7 (Mohs scale), Color: White to yellowish-tan, Luster: Vitreous to dull when weathered, Crystal structure: Hexagonal (trigonal system) in individual grains, Cleavage: None (conchoidal fracture), Specific gravity: 2.6 - 2.7

Formation & Geological History

Formed through the regional metamorphism of quartz sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together. This specimen appears water-worn, likely from a riverbed or glacial deposit.

Uses & Applications

Used in construction for road ballast, roofing granules, and as a decorative stone in landscaping. Historically used for stone tools due to its hardness and durability.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rocks during erosion, forming prominent ridges and peaks in mountain ranges. It is resistant to chemical weathering.

Field Identification & Locations

Identify in the field by its hardness (it will scratch glass and steel) and its crystalline, sugary appearance. Unlike sandstone, quartzite fractures through the grains rather than around them. Commonly found in ancient mountain belts.

Identified on: 4/25/2026

Mode: Standard