mineral

Chalcedony Geode Part (Agate/Quartz)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Grayish-white, translucent; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64

Hardness: 6
Color: Grayish-white, translucent
Luster: Waxy to vitreous

Identified June 21, 2026More mineral →

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Physical properties

Formation & geological history

Formed via the deposition of silica from groundwater in cavities of volcanic or sedimentary rocks. Over long periods, silica-rich fluids cool or evaporate, leaving behind layers of microcrystalline quartz.

Uses & applications

Used in jewelry (cabochons, beads), micro-precision bearings, as industrial abrasives, and as ornamental display pieces for collectors.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen without high magnification. When it forms in concentric layers, it is specifically called Agate.

Field identification & locations

Identified by its waxy luster, conchoidal (shell-like) fracture, and inability to be scratched by a steel knife. Commonly found in basaltic lava flows or as nodules in limestone.

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