Ferruginous Quartzite (Red Sandstone/Quartzite)

Physical Properties

Hardness: 7 (Mohs scale); Color: Reddish-brown, tan, and grey; Luster: Vitreous to dull; Crystal structure: Hexagonal (as quartz grains); Cleavage: None; Specific gravity: 2.6–2.7

Formation & Geological History

Formed from the metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. The reddish color is due to the presence of iron oxides like hematite or goethite during formation.

Uses & Applications

Used primarily in construction as crushed stone or road ballast. Varieties with attractive coloring are used for landscaping, decorative stone, and occasionally for lapidary work.

Geological Facts

Quartzite is so durable that it can survive long-term erosion better than almost any other rock. This specific specimen shows 'conchoidal' (glass-like) fractures, which is a hallmark of quartz-rich materials.

Field Identification & Locations

Identify in the field by its extreme hardness (it will easily scratch glass or steel) and its grainy, sandpaper-like texture that doesn't rub off. It is commonly found in mountain ranges and ancient shield areas.

Identified on: 4/15/2026

Mode: Standard