mineral

Ferruginous Quartz

Silicon Dioxide (SiO2) with Iron Oxide (Fe2O3) inclusions

Hardness: 7 on Mohs scale; Color: Milky white to translucent with reddish-brown or yellowish-orange staining; Luster: Vitreous (glassy); Crystal Structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Luster: Vitreous (glassy)

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed through hydrothermal processes where silica-rich fluids crystallize in rock fractures. The reddish-brown matrix and staining are caused by secondary iron oxide minerals (such as limonite or hematite) leaching into the quartz during or after formation.

Uses & applications

Primarily used as a decorative specimen for rock collectors. Quartz itself is used in electronics (oscillator crystals), glass making, and abrasives, though iron-stained specimens are less pure for high-end industrial use.

Geological facts

Also known as 'Iron Quartz' or 'Limonitic Quartz.' The iron staining can sometimes be removed with chemical cleaners like oxalic acid to reveal the clear quartz underneath, but collectors often prefer the natural 'rusty' character for its aesthetic appeal.

Field identification & locations

Identify in the field by its ability to scratch glass (hardness of 7), glassy appearance of the white parts, and the distinctive rusty, earthy crust of iron oxide. It is extremely common in pegmatites, mountain ranges, and gravel pits globally.

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