Ferruginous Quartz (Iron-stained Quartzite)

Physical Properties

Hardness: 7 (Mohs scale), Color: Tan to reddish-orange with white interiors, Luster: Vitreous to dull (if weathered), Crystal Structure: Trigonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize. The orange/red staining occurs as iron-rich groundwater percolates through cracks in the rock over geological time.

Uses & Applications

Commonly used in construction as aggregate or road base. Rounded specimens like this are often used in landscaping or rock tumbling. Some high-purity varieties are used in glass manufacturing.

Geological Facts

Quartz is the most abundant mineral in the Earth's continental crust. These water-worn river rocks can travel hundreds of miles from their original source, becoming smoothed and rounded through abrasion.

Field Identification & Locations

Identify in the field by its hardness (it will scratch glass) and its lack of reaction to acid. Look for the granular, 'sugar-like' texture typical of quartzite combined with orange staining on the outer rind.

Identified on: 4/21/2026

Mode: Standard