Quartzite Pebble

Physical Properties

Hardness: 7 on Mohs scale; Color: yellowish-tan to grey; Luster: vitreous to dull; Crystal structure: hexagonal/trigonal (microcrystalline); Cleavage: none; Specific gravity: ~2.65

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the original quartz grains to recrystallize into an interlocking mosaic.

Uses & Applications

Used primarily as construction aggregate, railway ballast, and occasionally as decorative stones or in landscaping.

Geological Facts

Quartzite is so tough that it usually breaks through the quartz grains rather than along their boundaries, unlike sandstone which breaks between the grains.

Field Identification & Locations

Identify in the field by its hardness (will scratch glass) and lack of reaction to acid. Commonly found in riverbeds or glacial deposits as rounded cobbles.

Identified on: 5/5/2026

Mode: Standard