sedimentary

Dragon Stone

Argillaceous Sedimentary Rock (Ohko Stone)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale), Color: Brownish-gold, grey, and ochre, Luster: Dull/Earthy, Crystal Structure: Amorphous/Microcrystalline, Specific Gravity: 2.3-2.6

Identified March 26, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs scale), Color: Brownish-gold, grey, and ochre, Luster: Dull/Earthy, Crystal Structure: Amorphous/Microcrystalline, Specific Gravity: 2.3-2.6

Formation & geological history

Formed through millions of years of water erosion and pressure on ancient lake or river beds, primarily during the Cretaceous period. The unique 'scaly' texture is created by the selective weathering of softer clay minerals while harder compressed silt remains.

Uses & applications

Primarily used in 'aquascaping' for freshwater aquariums due to its inert quality (doesn't affect pH) and interesting crevices. Also used in terrariums and miniature landscapes.

Geological facts

Dragon stone is famous for its appearance which resembles dragon scales. While it looks very rugged and hard, it is actually quite fragile and can be easily carved or broken by hand when wet as it is composed largely of hardened clay and silt.

Field identification & locations

Identify in the field by its distinct cratered, porous surface and brittle, flaky texture when scraped. It is almost exclusively sourced from Japan, specifically found in mountain streams and coastal areas. Collectors should wash it thoroughly as the holes are often packed with dried mud.