mineral

Chalcedony (Botryoidal or Tumbled)

Chalcedony (SiO₂)

Hardness: 6.5-7 (Mohs scale); Color: Translucent grayish-white to tan; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Trigonal/Monoclinic); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.64.

Hardness: 6
Color: Translucent grayish-white to tan
Luster: Waxy to vitreous

Identified March 13, 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 by the precipitation of water-rich silica solutions in cavities of volcanic and sedimentary rocks. This specimen likely formed as an agate or chalcedony nodule within an igneous gas pocket (amygdule) or as a replacement of organic material.

Uses & applications

Used primarily in lapidary work for tumbled stones, cabochons, and beads. Historically used for making tools due to its hardness and sharp edges (knapping). Industrial uses include abrasive polishing.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen with a standard microscope. It is the broad category into which Agate, Jasper, Carnelian, and Onyx are classified.

Field identification & locations

Identify in the field by its translucency (light passes through edges), waxy texture when wet, and lack of visible crystal faces. Found globally in riverbeds, desert pavements, and volcanic regions like Oregon, India, and Brazil.

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