Ferruginous Quartzite (Red Quartz)

Physical Properties

Hardness: 7 (Mohs scale); Color: Varying shades of gray, white, and rusty red/brown; Luster: Vitreous to dull; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7

Formation & Geological History

Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure Recrystallize quartz grains. The red staining is caused by iron oxides (hematite) leaching into the rock. They are commonly found in Precambrian formations over 500 million years old.

Uses & Applications

Used primarily as construction aggregate, railway ballast, and occasionally as decorative stone or in lapidary work for tumbled stones.

Geological Facts

Quartzite is so tough that it often survives intense glacial movements and water erosion, which is why it is frequently found as rounded river or beach cobbles like this specimen.

Field Identification & Locations

Identify by its ability to scratch glass and its grainy, sandpaper-like texture that has been fused into a crystalline mass. It is commonly found in mountain ranges or glacial till deposits.

Identified on: 4/18/2026

Mode: Standard