mineral

Ferruginous Quartz

Silicon Dioxide with Hematite/Limonite impurities (SiO2 + Fe2O3)

Hardness: 7 (Mohs scale); Color: White or clear base with reddish-brown staining; Luster: Vitreous (glassy); Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 (Mohs scale)
Color: White or clear base with reddish-brown staining
Luster: Vitreous (glassy)

Identified March 21, 2026More mineral →

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Physical properties

Formation & geological history

Formed in hydrothermal veins or pegmatites when silica-rich fluids cool and crystallize. The reddish staining occurs when iron oxide (hematite) or hydroxide (limonite) is present during growth or leaches into fractures in the quartz over geological time.

Uses & applications

Common specimens are used for landscaping, as aquarium decor, or as meditation stones. Higher-quality iron-quartz (Harlequin Quartz) is used in jewelry and lapidary arts.

Geological facts

Also known as 'Hematoid Quartz' or 'Fire Quartz' by collectors. The iron inclusions can appear as internal 'stars' or external coatings depending on whether the iron was trapped during the crystal's initial formation or added later via groundwater.

Field identification & locations

Identify in the field by its ability to scratch glass (high hardness), glassy luster, and the presence of rust-colored streaks that do not wash off. Found globally in areas with silica-rich soil and high iron content, such as Brazil, Madagascar, and parts of the United States.

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