Ferruginous Quartz

Physical Properties

Hardness: 7 (Mohs scale); Color: White to grey with reddish-brown staining; Luster: Vitreous to greasy; Crystal Structure: Hexagonal; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65

Formation & Geological History

Formed through hydrothermal processes where silica-rich fluids permeate cracks in existing rock. The reddish staining occurs as iron minerals like hematite or goethite are introduced during or after the crystal formation.

Uses & Applications

Commonly collected as a mineral specimen. If the staining is attractive, it can be used for lapidary work such as cabochons or landscaping stone.

Geological Facts

Also known as Eisenkiesel, this variety of quartz gets its name from the Latin word for iron. It is one of the most common mineral occurrences in the Earth's crust due to the abundance of both silicon and iron.

Field Identification & Locations

Identify in the field by its high hardness (will scratch glass), lack of cleavage, and the rusty red-brown staining that cannot be washed off. Found globally in a variety of geological settings, especially mining tailings and pegmatites.

Identified on: 4/20/2026

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