mineral

Chalcedony

Silicon dioxide (SiO2) - Cryptocrystalline Quartz

Hardness: 6.5-7 on Mohs scale. Color: Translucent tan, smoky, or grayish-brown. Luster: Waxy to vitreous. Crystal structure: Trigonal (microscopic). Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.64.

Hardness: 6
Color: Translucent tan, smoky, or grayish-brown
Luster: Waxy to vitreous

Identified April 4, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed from the deposition of silica from water solutions in volcanic cavities (vesicles) or sedimentary environments like petrified wood. Can range from recently formed to millions of years old.

Uses & applications

Commonly used for semi-precious jewelry, decorative carvings, tumbling for rock collections, and historically for stone tools due to its sharp conchoidal fracture.

Geological facts

Chalcedony is actually a broad category that includes more specific varieties like agate, onyx, and carnelian. It was used in the ancient world for cylinder seals and amulets.

Field identification & locations

Identify in the field by its waxy luster, smooth conchoidal fracture, and translucency when held to light. Frequently found in riverbeds, desert pavements, and volcanic regions.

Other mineral specimens

See all

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

Green Apatite on Albite

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

mineral

Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral