mineral

Green Opal

Hydrated amorphous silica (SiO2·nH2O)

Hardness: 5.5-6.5 on the Mohs scale, Color: Pale green to translucent greenish-white, Luster: Vitreous to waxy, Crystal structure: Amorphous (non-crystalline), Cleavage: None, Specific gravity: 1.90-2.30

Hardness: 5

Identified July 31, 2026More mineral →

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Physical properties

Formation & geological history

Formed from a solution of silicon dioxide and water at relatively low temperatures, often filling cracks or voids in various types of rock, commonly associated with volcanic ash deposits and weathering environments.

Uses & applications

Widely used in jewelry, lapidary arts, and ornamental carvings; highly sought after by crystal collectors.

Geological facts

Unlike many other gemstones, opal contains a significant amount of trapped water, which can range from 3% to 21% by weight. Green opal is particularly noted for its soothing, pastel tones and lack of traditional play-of-color.

Field identification & locations

Identified by its amorphous, smooth, kidney-like (botryoidal or conchoidal) fracture surface, waxy luster, and lower hardness than quartz. Found worldwide, including notable deposits in Madagascar, Peru, Australia, and the USA.