River Quartzite (River Rock)

Physical Properties

Hardness: 7 on Mohs scale; Color: Yellowish-brown, tan, and grey with iron staining; Luster: Dull to waxy; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6-2.7

Formation & Geological History

Formed through the regional metamorphism of quartz-rich sandstone. The intense heat and pressure cause the quartz grains to recrystallize and fuse together. This specific specimen has been further shaped and rounded by fluvial (river) erosion over thousands of years.

Uses & Applications

Commonly used in landscaping (decorative river rock), construction aggregate, and occasionally as a low-cost material for tumbling and lapidary practice for beginners.

Geological Facts

Quartzite is so hard and chemically resistant that it frequently forms ridges and hilltop caps because it resists weathering better than surrounding rocks. It can scratch glass easily.

Field Identification & Locations

Identify in the field by its hardness (it should scratch a steel knife blade) and its grainy, sugary texture when broken. River-worn specimens like this are found in ancient or active riverbeds worldwide. Look for a smooth, rounded surface with a slight translucent quality when held to light.

Identified on: 4/15/2026

Mode: Standard