mineral

Green Opal

Hydrated silica (SiO2 n nH2O)

Hardness: 5.5-6.5 on Mohs scale; Color: Olive green to lime green with potential yellow or brown hues; Luster: Vitreous to waxy; Crystal structure: Amorphous; Cleavage: None; Specific Gravity: 1.9-2.3

Hardness: 5
Luster: Vitreous to waxy

Identified May 9, 2026More mineral →

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Physical properties

Formation & geological history

Formed from silica-rich groundwater that seeps into cracks and cavities in volcanic or sedimentary rocks. Over millions of years, the water evaporates, leaving behind silica deposits that harden into common opal. Many green specimens are from the Tertiary to Quaternary periods.

Uses & applications

Primarily used for lapidary work, jewelry (cabs or beads), decorative carvings, and as pocket stones in the metaphysical/collecting markets.

Geological facts

Unlike 'precious' opal, green opal is 'common' opal because it lacks the play-of-color caused by ordered silica spheres. The green color is typically caused by inclusions of minerals like nickel (chrysopal) or chlorite.

Field identification & locations

Look for a smooth, waxy feel and lack of crystal structure. Common locations include Madagascar, Tanzania, Australia, and Brazil. Collectors should look for vibrant color and internal translucency.