Yellow Quartzite (River Pebble)

Physical Properties

Hardness: 7 (Mohs). Color: Yellowish-tan to creamy white. Luster: Vitreous to dull. Crystal Structure: Trigonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.63–2.65.

Formation & Geological History

Formed when quartz-rich sandstone is subjected to heat and pressure during regional metamorphism. This specific specimen has been further shaped and smoothed by fluvial or alluvial erosion (water action) in a river or beach environment.

Uses & Applications

Primary use is industrial (crushed stone for construction and railway ballast). Smoothed pebbles are often used in decorative landscaping, aquariums, and crafts.

Geological Facts

Quartzite is often harder than the sandstone it originated from; while sandstone feels gritty and breaks around sand grains, quartzite breaks through the grains because the silica cement is as strong as the grains themselves.

Field Identification & Locations

Identify in the field by its hardness (it will scratch glass) and its dense, sugary or crystalline texture. Common in ancient mountain belts and riverbeds originating from mountainous terrain.

Identified on: 4/14/2026

Mode: Standard