mineral

Wild Horse Magnesite

Magnesite with Hematite inclusions (MgCO3)

Hardness: 3.5-4.5 (Mohs scale); Color: White or cream with reddish-brown to dark brown matrix; Luster: Sub-vitreous to dull/earthy; Crystal Structure: Trigonal; Cleavage: Perfect rhombohedral; Specific Gravity: 3.0

Hardness: 3
Color: White or cream with reddish-brown to dark brown matrix
Luster: Sub-vitreous to dull/earthy

Identified March 24, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the alteration of magnesium-rich rocks (ultramafic) or the metamorphism of magnesium-bearing sediments. Often found in hydrothermal veins. The specific pattern in this specimen is created by iron oxide seepage.

Uses & applications

Primarily used in jewelry for cabochons and beads. In industrial form, magnesite is used to produce magnesium oxide for refractory bricks and pharmaceuticals.

Geological facts

Wild Horse Magnesite is specifically associated with the Gila Wilderness area in Southern Arizona. It is often mistakenly called 'Wild Horse Turquoise,' but it contains no copper and is therefore not turquoise.

Field identification & locations

Identify by its distinct white-to-chocolate brown contrast. In the field, look for a heavy, chalky white stone that doesn't scratch easily with a fingernail but is softer than quartz. Commonly found in Arizona and Nevada, USA.

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