Mineral

Iron-stained Quartz (with Limonite/Hematite)

Silicon Dioxide (SiO2) with Iron Oxide inclusions (FeO(OH) or Fe2O3)

Hardness: 7 (Mohs scale); Color: Rusty orange, brown, and tan over a white/clear base; Luster: Vitreous to dull/earthy; Crystal Structure: Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Rusty orange, brown, and tan over a white/clear base
Luster: Vitreous to dull/earthy

Identified March 26, 2026More mineral →

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Physical properties

Formation & geological history

Formed in hydrothermal veins or as a secondary mineral precipitate in sedimentary environments. Iron staining occurs when groundwater rich in iron oxides permeates the host quartz. Ages vary from Precambrian to recent.

Uses & applications

Primarily of interest to mineral collectors or as an industrial source for iron/silica. Often treated with acid to clean the quartz for decorative use.

Geological facts

Commonly known by prospectors as 'iron hat' or 'gossan' when found in large outcrops, it is often a field indicator for deeper mineral deposits such as gold or copper.

Field identification & locations

Identify in the field by its high hardness (scratches glass), rust-colored staining that cannot be easily washed off, and lack of cleavage. Found globally in mountainous and mining regions.

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