sedimentary
Dragon Stone
Argillaceous Sedimentary Rock (Ohko Stone)
Hardness: 3-4 (Mohs scale), Color: Brownish-gold, grey, and ochre, Luster: Dull/Earthy, Crystal Structure: Amorphous/Microcrystalline, Specific Gravity: 2.3-2.6
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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.
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