Red Quartzite / Ferruginous Quartzite

Physical Properties

Hardness: 7 (Mohs scale); Color: Pinkish-red to reddish-brown due to iron oxide (hematite); Luster: Dull to vitreous; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.8

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, usually in orogenic (mountain-building) belts. The red color suggests the presence of iron oxide during or after the deposition of the original sediment.

Uses & Applications

Used as crushed stone for road construction, railway ballast, and as a decorative stone in landscaping or lapidary work (when polished). High-purity quartzite is used to produce silica sand for glass making.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rock, forming prominent ridges and hills. It is one of the most durable rocks found at the Earth's surface and was sometimes used by prehistoric humans to create stone tools when flint was unavailable.

Field Identification & Locations

Identify by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sandpaper-like texture that has been fused into a solid mass. It breaks across grains rather than around them, unlike sandstone. Common in glacial till or riverbeds in the Northern Hemisphere.

Identified on: 4/14/2026

Mode: Standard