Red Quartzite (River Stone)

Physical Properties

Hardness: 7 on Mohs scale; Color: Reddish-brown due to iron oxide impurities; Luster: Vitreous to waxy (when wet/polished); Crystal Structure: Non-foliated, granular; Specific Gravity: 2.6-2.7.

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. This specific specimen shows rounding from fluvial erosion (river action).

Uses & Applications

Used as decorative landscaping stone, in construction as aggregate, for lapidary work/polishing, and historically as a tool stone due to its extreme hardness.

Geological Facts

Quartzite is so tough that it often survives intense weathering that destroys surrounding rocks; it breaks across the quartz grains rather than around them, unlike its precursor sandstone.

Field Identification & Locations

Identify in the field by its hardness (will easily scratch glass) and granular texture that looks like sugar. Common in riverbeds and mountainous glacial tills.

Identified on: 4/28/2026

Mode: Standard