mineral
Yellow chalcedony (likely polished/tumbled pieces)
Microcrystalline quartz, SiO₂; commonly called yellow jasper or silicified limestone depending on exact texture
AI-generated identification · may be incorrectTypically Mohs 6.5–7, pale yellow to ochre with gray-brown banding, waxy to dull luster, cryptocrystalline structure, and no visible cleavage; specific gravity about 2.6. The pieces appear cut or naturally flattened and polished, with iron-oxide staining and possible sedimentary inclusions.
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Physical properties
Typically Mohs 6.5–7, pale yellow to ochre with gray-brown banding, waxy to dull luster, cryptocrystalline structure, and no visible cleavage; specific gravity about 2.6. The pieces appear cut or naturally flattened and polished, with iron-oxide staining and possible sedimentary inclusions.
Formation & geological history
Forms when silica-rich fluids fill cavities, fractures, or porous sediment and later harden into chalcedony/jasper; the banding may reflect changing fluid chemistry. Exact geological age and locality cannot be determined from the photograph.
Uses & applications
Used for cabochons, beads, carvings, lapidary specimens, and decorative stone; comparable common pieces generally have modest value.
Geological facts
Chalcedony is quartz made of extremely small interlocking crystals, so it often breaks with a smooth, curved fracture rather than showing quartz crystal faces.
Field identification & locations
Identify by its waxy appearance, very high hardness, fine-grained texture, and inability to scratch it with a steel knife; vinegar will not fizz unless carbonate matrix is present. Similar material occurs worldwide, including Brazil, India, Madagascar, Mexico, and the western United States.
