mineral

Chalcedony Agate Nodule

Silicon Dioxide (SiO2)

Mohs hardness 6.5-7, translucent to sub-translucent, waxy to vitreous luster, microcrystalline quartz structure, conchoidal fracture, specific gravity 2.58-2.64. Displaying warm orange, amber, and light tan hues with fine concentric banding and a hollow geodic cavity.

Identified July 22, 2026More mineral →

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Physical properties

Formation & geological history

Formed by the low-temperature deposition of silica-rich hydrothermal fluids in gas cavities (vesicles) within volcanic rocks such as basalt or rhyolite, or in sedimentary beds over millions of years.

Uses & applications

Used extensively in jewelry making, cabochon cutting, lapidary arts, decorative carvings, and as a popular collectible specimen.

Geological facts

Agate nodules often contain inner cavities lined with tiny quartz crystals (drusy) or exhibit chalcedony desert-rose style swirls, formed as layer upon layer of silica gel precipitated slowly within ancient volcanic rocks.

Field identification & locations

Can be identified by its distinctive waxy luster, conchoidal fracture surfaces, curved concentric banding patterns, and translucency when held up to a light source. Commonly found in basaltic gravel deposits and river beds worldwide.