mineral

Agate (Puddingstone style)

Silicon Dioxide (SiO2) with impurities

Hardness: 6.5-7 on Mohs scale. Color: Translucent grey, tan, and brown with rounded inclusions. Luster: Vitreous to waxy when wet/polished. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Translucent grey, tan, and brown with rounded inclusions
Luster: Vitreous to waxy when wet/polished

Identified June 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed as secondary deposits in volcanic cavities or sedimentary pockets where silica-rich groundwater precipitates over long periods, often filling in around existing pebbles to create a conglomerate-like appearance.

Uses & applications

Primarily used for lapidary work, jewelry (cabochons), as decorative stones, or for rock tumbling and collecting.

Geological facts

Agates are a variety of chalcedony. This specific piece shows characteristics of a 'puddingstone' or conglomerate agate, where distinct rounded grain inclusions are cemented in a chalcedony matrix.

Field identification & locations

Identify by its waxy luster and toughness. It won't be scratched by a steel knife. Commonly found in riverbeds, glacial till, or volcanic regions such as the Great Lakes area or the Pacific Northwest.

Other mineral specimens

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral