mineral

Agate (Chalcedony slice)

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Translucent white, grey, beige with brown banding; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58-2.64

Hardness: 6
Color: Translucent white, grey, beige with brown banding
Luster: Waxy to vitreous

Identified May 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed by the deposition of silica from groundwater in the cavities (vesicles) of igneous rocks, particularly volcanic lavas. Most are of Cenozoic to Mesozoic age.

Uses & applications

Commonly used for lapidary arts, jewelry, decorative coasters, bookends, and collection specimens. Historically used for making hardstone carvings.

Geological facts

The name 'Agate' comes from the Achates River in Sicily, where agates were first discovered by the Greek philosopher Theophrastus around the 4th century BC.

Field identification & locations

Identify in the field by its translucent nature when held to light and its characteristic concentric or parallel banding within a nodule or geode. Found globally, especially in Brazil, Uruguay, and the US (Great Lakes, Montana).

Other mineral specimens

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

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

Biotite Schist

Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]

metamorphic

Green Apatite on Albite

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

mineral