sedimentary

Green Onyx (Carved Mushroom)

Calcite / Banded Calcite (often commercially sold as 'Mexican Onyx')

Hardness of 3 on the Mohs scale, predominantly green with brownish-orange banding, vitreous to waxy luster, massive or microcrystalline structure, perfect rhombohedral cleavage, specific gravity around 2.71

Identified July 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the precipitation of calcium carbonate from mineral-rich waters in caves, hot springs, or limestone cavities, creating stalactites, stalagmites, or flowstone deposits over thousands to millions of years

Uses & applications

Carved into decorative objects, figurines, and home decor items like the mushroom shown in the image; also used for interior design accents and lapidary work

Geological facts

Geologically, this stone is actually banded calcite or aragonite rather than true scientific onyx, which is a cryptocrystalline form of quartz. The green color typically comes from trace amounts of nickel, chromium, or iron compounds

Field identification & locations

Easily identified by its characteristic banding, polished glossy finish, and relative softness (can be scratched with a knife or copper penny); commonly sourced from countries like Pakistan, Mexico, and China

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