mineral
Chalcedony / Agate Nodule with Druzy Cavity
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness 6.5-7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, translucent to opaque grayish-tan coloring with micro-druzy quartz crystals lining a small vug or hollow void.
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Physical properties
Hardness 6.5-7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, translucent to opaque grayish-tan coloring with micro-druzy quartz crystals lining a small vug or hollow void.
Formation & geological history
Formed through the deposition of silica-rich hydrothermal groundwater into gas pockets (vesicles) within volcanic basalt or sedimentary limestone cavities. Geological age varies widely from Paleozoic to Tertiary.
Uses & applications
Commonly collected as lapidary rough, tumbled, carved into cabochons for jewelry, or kept as natural rough specimens by mineral collectors.
Geological facts
Vugs within chalcedony nodules often preserve hollow centers that can grow sparkling tiny quartz crystals (druzy quartz), giving the specimen a miniature geode-like interior.
Field identification & locations
Identified in the field by its hardness (scratches glass and steel), lack of cleavage, waxy/chalcedonic sheen, and internal micro-crystal cavities. Commonly found in river gravels, glacial drift deposits, and volcanic rock outcrops.
