mineral
Polished dendritic jasper or agate
Microcrystalline quartz (chalcedony), SiO₂, with iron/manganese oxide dendrites and earthy inclusions
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque cream, yellow, tan, and gray-brown with black branching or mossy inclusions; waxy to glassy luster after polishing, cryptocrystalline structure, and no visible cleavage. The rounded form appears polished or tumbled.
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Physical properties
Hardness about 6.5–7 Mohs; opaque cream, yellow, tan, and gray-brown with black branching or mossy inclusions; waxy to glassy luster after polishing, cryptocrystalline structure, and no visible cleavage. The rounded form appears polished or tumbled.
Formation & geological history
Silica-rich groundwater filled cavities and fractures in volcanic or sedimentary host rock, while iron and manganese oxides created the dark patterns; individual deposits range from Paleozoic to Cenozoic age. Similar material occurs worldwide, including India, Madagascar, Indonesia, Mexico, and the western United States.
Uses & applications
Used for cabochons, beads, carvings, worry stones, and lapidary collectibles; rarely used as aggregate or ornamental stone. Value is mainly determined by pattern, polish, color, and size.
Geological facts
The branching markings are often called dendrites, though they are mineral-growth patterns rather than fossils or plant remains. Exact identification as jasper versus agate requires examination of translucency and texture.
Field identification & locations
Identify by its very fine grain, excellent polish, hardness, and natural brown-black inclusions; it should resist scratching from a steel knife. Common commercial pieces are sold as dendritic jasper, picture jasper, or moss agate depending on appearance.
