mineral
Botryoidal chalcedony (likely agate/jasper nodule)
Microcrystalline quartz, SiO₂; commonly mixed with iron oxides and clay minerals
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; rounded grape-like surfaces, cream, tan, orange, and green-brown colors, and a waxy to dull luster. It has cryptocrystalline quartz structure, no cleavage, conchoidal fracture, and specific gravity near 2.6.
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Physical properties
Hardness about 6.5–7 Mohs; rounded grape-like surfaces, cream, tan, orange, and green-brown colors, and a waxy to dull luster. It has cryptocrystalline quartz structure, no cleavage, conchoidal fracture, and specific gravity near 2.6.
Formation & geological history
Forms when silica-rich groundwater deposits concentric or botryoidal layers in cavities and fractures of volcanic rock. The specimen’s precise geological age cannot be determined from the photograph; such nodules occur from ancient to recent volcanic environments.
Uses & applications
Used as a lapidary stone, cabochon, carving material, and collector specimen; attractive material may be polished for jewelry or décor.
Geological facts
Botryoidal means clustered into rounded, bubble-like lobes; iron and manganese impurities create the orange, brown, and green coloration.
Field identification & locations
Identify by its very hard, waxy, curved surfaces and inability to scratch with a steel knife; glass should not scratch it. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and volcanic regions worldwide.
