mineral

Agate (specifically Chalcedony nodule)

Silicon Dioxide (SiO2)

Hardness: 6.5–7 on Mohs scale. Color: Translucent white to creamy tan with reddish inclusions. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (hexagonal/trigonal). Cleavage: None (conchoidal fracture). Specific gravity: 2.6–2.7.

Hardness: 6
Color: Translucent white to creamy tan with reddish inclusions
Luster: Waxy to vitreous

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed in volcanic or sedimentary rocks over millions of years (often Cenozoic era). Silica-rich fluids deposit layers within rock cavities or gas bubbles (vesicles), hardening into nodules.

Uses & applications

Used in gemstone carvings, jewelry (cabochons), as burnishing tools in leatherworking, and as decorative pocket stones for collectors.

Geological facts

Agates are traditionally used as birthstones for June. This specific specimen appears to be a 'river-worn' or 'tumbled' nodule, where natural water action has smoothed its surface into a pebble shape.

Field identification & locations

Identify in the field by its translucency (light passes through the edges), waxy feel, and lack of visible grains. Common in riverbeds, glacial till, and volcanic regions like Lake Superior or the Pacific Northwest.

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