mineral

Ferruginous Quartz (Red Jasper/Carnelian Agate)

Silicon Dioxide (SiO2) with Iron Oxide inclusions

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, orange-brown, earthy amber; Luster: Waxy to vitreous; Crystal structure: Hexagonal (microcrystalline/cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91

Hardness: 6
Color: Reddish-brown, orange-brown, earthy amber
Luster: Waxy to vitreous

Identified June 20, 2026More mineral →

Explore Ferruginous Quartz (Red Jasper/Carnelian Agate) in the encyclopedia →

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Physical properties

Formation & geological history

Formed via precipitation of silica-rich fluids in volcanic cavities or sedimentary environments. The red coloration is due to the presence of Hematite or Limonite (iron oxide) impurities infused during formation. Many specimens are found as river-worn nodules from the Cenozoic era.

Uses & applications

Used frequently in lapidary work for cabochons, beads, and carvings. Also used as a decorative landscaping stone and as a popular specimen for beginner rock hounds and collectors due to its durability.

Geological facts

This type of cryptocrystalline quartz has been used since antiquity for royal seals and amulets. The term 'ferruginous' comes from the Latin 'ferrum', meaning iron, which gives the stone its characteristic warm hue.

Field identification & locations

Identify by its hardness (will scratch glass), conchoidal (shell-like) fracture pattern, and waxy texture when wet or polished. Often found in riverbeds, gravel pits, and desert washes throughout the Western United States, Brazil, and India.