mineral

Ferruginous Quartz (Red Quartz)

Silicon Dioxide (SiO2) with Hematite/Limonite impurities

Hardness: 7.0 on Mohs scale; Color: Reddish-brown to orange-tan; Luster: Vitreous to waxy; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7
Color: Reddish-brown to orange-tan
Luster: Vitreous to waxy

Identified March 30, 2026More mineral →

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Physical properties

Hardness: 7.0 on Mohs scale; Color: Reddish-brown to orange-tan; Luster: Vitreous to waxy; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Formation & geological history

Formed through hydrothermal processes where silica-rich fluids crystallize. The reddish color comes from the inclusion of iron oxides (hematite or limonite) during or after the crystal growth. Smooth, rounded specimens like this are typically shaped by fluvial (river) or glacial erosion over thousands of years.

Uses & applications

Used primarily for decorative purposes, lapidary work (tumbled stones), and as a collector's specimen. In industry, pure quartz is used for glassmaking and electronics, but colored varieties are reserved for ornamentation.

Geological facts

Red quartz is often referred to as 'Iron Quartz.' When the iron content is very high, it is sometimes called 'Eisenkiesel.' This specific specimen is a 'river pebble,' meaning its smooth surface was naturally polished by the abrasive action of water and sand in a stream bed.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its lack of visible grains compared to sandstone, and its translucent to opaque reddish-brown hue. It is found globally in areas with high quartz concentrations, such as the Appalachian Mountains in the US, Brazil, and Madagascar.

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