Quartzite (River Pebble)

Physical Properties

Hardness: 7 (Mohs scale). Color: White to grayish-tan with iron staining. Luster: Vitreous to waxy. Crystal Structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.63 - 2.65.

Formation & Geological History

Formed through the metamorphism of quartz sandstone under high heat and pressure. This specific specimen has been further shaped into a smooth pebble by fluvial (river) or glacial transport erosion.

Uses & Applications

Used as aggregate in construction, railway ballast, and road base. Polished stones are used in landscaping, floral arrangements, and as decorative pocket stones.

Geological Facts

Quartzite is so hard that it can scratch glass and steel. It is one of the most durable rocks on Earth, which is why it often survives as smooth pebbles in riverbeds long after softer rocks have eroded away.

Field Identification & Locations

Identify in the field by its extreme hardness and sugary or crystalline appearance when freshly broken. Found globally in ancient mountain belts and river basins.

Identified on: 4/26/2026

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