Quartzite Pebble (with Iron Staining)

Physical Properties

Hardness: 7 (Mohs scale), Color: White, gray, or tan with yellowish-brown iron oxidation; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Specific gravity: 2.6-2.7. It is smooth and water-worn.

Formation & Geological History

Formed from the metamorphism of quartz sandstone under intense heat and pressure, causing the original quartz grains to recrystallize into a dense, interlocking matrix. This specific specimen has been rounded by river or beach water transport.

Uses & Applications

Used as aggregate in construction, road ballast, and decoratively in landscaping. High-purity quartzite is used in glassmaking and electronics.

Geological Facts

Quartzite is so hard and chemically resistant that it often remains as caps on mountains and ridges after softer rocks have eroded away. The yellow/orange coating on this specimen is likely limonite or goethite, minerals formed by the oxidation of iron.

Field Identification & Locations

Identify by its ability to scratch glass (hardness) and the lack of reaction to acid. It can be found in riverbeds, beaches, and glaciated areas globally. For collectors, it is a common but beautiful example of geological wear.

Identified on: 4/13/2026

Mode: Standard