mineral

Agate (specifically Botswana or Lake Superior style chalcedony)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs); Color: translucent brown to tan; Luster: waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: none; Conchoidal fracture; Specific gravity: 2.58-2.64

Hardness: 6
Color: translucent brown to tan
Luster: waxy to vitreous

Identified April 19, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: translucent brown to tan; Luster: waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: none; Conchoidal fracture; Specific gravity: 2.58-2.64

Formation & geological history

Formed as a secondary deposit in volcanic rock cavities (vesicles) from silica-rich groundwater. Over millions of years, the silica precipitates into concentric layers or microcrystalline masses.

Uses & applications

Used primarily in lapidary arts for jewelry, beads, and cabochons. Historically used for mortar and pestles due to its hardness and resistance to chemicals.

Geological facts

Agates often feature 'eyes' or banding that is only visible when sliced or polished. They are a variety of chalcedony and are found inside geodes or as nodules in riverbeds.

Field identification & locations

Identify by its translucent quality and waxy surface when wet. Unlike common river stones, agates allow light to pass through the edges. Frequently found in glacial till, river beds, and gravel pits.

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