Ferruginous Quartz

Physical Properties

Hardness: 7 on Mohs scale; Color: Reddish-orange, brown, or tan; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None; Specific gravity: ~2.65

Formation & Geological History

Formed through the cooling of silica-rich hydrothermal fluids or within sedimentary environments where iron oxides (like hematite or goethite) permeate the quartz matrix. This specimen appears water-worn and smoothed by alluvial processes.

Uses & Applications

Used primarily in lapidary work for cabochons and beads, as well as in landscaping or as a collectible 'pocket stone' due to its color and durability.

Geological Facts

Also known as 'Eisenkiesel' in German, meaning 'iron flint.' The red color is not part of the quartz itself but is caused by microscopic particles of iron minerals trapped inside or coating the grain boundaries.

Field Identification & Locations

Identify in the field by its hardness (it will scratch glass), its lack of cleavage (conchoidal fracture), and its smooth, rounded river-stone texture. It is a common find in riverbeds and shoreline gravels globally.

Identified on: 4/17/2026

Mode: Standard