mineral

Ferruginous Quartz (Iron-stained Quartz)

Silicon Dioxide with Iron Oxide (SiO2 + Fe2O3)

Hardness: 7 (Mohs scale); Color: Tan, brownish-orange, or yellow due to limonite/hematite staining; Luster: Vitreous to dull (if weathered); Crystal Structure: Hexagonal (Trigonal); Cleavage: None; Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Luster: Vitreous to dull (if weathered)

Identified April 5, 2026More mineral →

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Physical properties

Formation & geological history

Formed in hydrothermal veins or as a secondary mineral deposit where groundwater rich in iron oxide leaches into the micro-fractures of existing quartz specimens. These can be found in a variety of geological ages from Precambrian to recent.

Uses & applications

Used primarily as decorative landscaping stones, road base, or aggregate. Highly translucent or well-crystallized pieces (often called 'Limonite Quartz') are valued by mineral collectors.

Geological facts

The orange or brown color is not part of the internal mineral structure but is a surface coating or infusion into micro-cracks. If soaked in an oxalic acid solution, the iron staining often dissolves, revealing white or clear quartz underneath.

Field identification & locations

Identify in the field by its high hardness (it will scratch glass) and its orange-brown 'rusty' appearance. It is common in riverbeds, areas with high clay content, and old mining districts.

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