Ferruginous Quartz (Iron-stained Quartz)

Physical Properties

Hardness: 7 on Mohs scale; Color: Milky white and various shades of reddish-brown; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture; Specific gravity: Approximately 2.65.

Formation & Geological History

Formed through the crystallization of silica in hydrothermal veins or as a secondary mineral in sedimentary environments. The brown coloration is caused by the infiltration of iron oxide (hematite or limonite) into the cracks or crystal lattice during or after formation.

Uses & Applications

Common specimens are used primarily for lapidary work (tumbling, cabochons), educational collections, and ornamental decoration. High-quality varieties like Jasper or Carnelian are used in jewelry.

Geological Facts

Quartz is the second most abundant mineral in Earth's continental crust. Iron-stained quartz is sometimes mistakenly called 'River Jasper' when it appears as a water-worn river pebble like this specimen.

Field Identification & Locations

Identify by its hardness (it will scratch glass) and its waxy to glassy appearance despite the surface staining. It is commonly found in riverbeds, gravel pits, and mountain trails worldwide.

Identified on: 4/23/2026

Mode: Standard