Quartzite Pebble

Physical Properties

Hardness: 7 on Mohs scale. Color: Creamy white to pale yellow. Luster: Vitreous to dull. Crystal structure: Non-foliated, granular. Cleavage: Indistinct/none. Specific gravity: ~2.65.

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, the sand grains recrystallize and fuse together into a dense, hard rock. Typically associated with mountain-building events.

Uses & Applications

Used as a construction aggregate, in road metal, as a decorative stone in landscaping, and sometimes as a source of silica for glass manufacturing.

Geological Facts

Quartzite is so hard and dense that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike its parent rock, sandstone.

Field Identification & Locations

Identify in the field by its extreme hardness (it will easily scratch glass) and its sugary, crystalline surface. Common in river beds, beaches, and glaciated areas as smoothed pebbles.

Identified on: 4/19/2026

Mode: Standard