Quartzite (Iron-stained)

Physical Properties

Hardness: 7 on Mohs scale; Color: Tan to yellowish-orange due to iron staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture.

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. The iron staining occurs through weathering and groundwater infiltration.

Uses & Applications

Used primarily as crushed stone for road construction, railroad ballast, and as a decorative stone in landscaping or lapidary work.

Geological Facts

Quartzite is so tough that it often breaks through the individual quartz grains rather than around them, which distinguishes it from sandstone. Its resistance to chemical weathering makes it a prominent ridge-former in many mountain ranges.

Field Identification & Locations

Identify in the field by its extreme hardness (it will easily scratch glass) and lack of reaction to acid. It is commonly found in metamorphic terranes and as water-worn cobbles in riverbeds.

Identified on: 5/8/2026

Mode: Standard