Quartzite (River Pebble)

Physical Properties

Hardness: 7 on Mohs scale; Color: Tan, brown, or grayish-white (stained by iron oxides); Luster: Vitreous to dull; Structure: Granitoid/Grainy; Cleavage: None/Conchoidal fracture.

Formation & Geological History

Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been further shaped by fluvial erosion in a river or glacial environment during the Holocene or Pleistocene epochs.

Uses & Applications

Used in construction as road ballast, gravel, and in industrial manufacturing as a source of silica. Smooth specimens are often used in decorative landscaping or as garden mulch.

Geological Facts

Quartzite is so hard that it will scratch glass. It is one of the most durable rocks on Earth's surface and often remains as 'leftover' pebbles after softer rocks have eroded away.

Field Identification & Locations

Identify in the field by its extreme hardness and sugary, crystalline texture when broken. Commonly found in riverbeds, conglomerate outcrops, and glacial tills.

Identified on: 4/22/2026

Mode: Standard