mineral

Botryoidal Chalcedony (Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs, Color: Yellowish-brown to tan, Luster: Waxy to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.6

Hardness: 6

Identified April 1, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 6.5-7 Mohs, Color: Yellowish-brown to tan, Luster: Waxy to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.6

Formation & geological history

Formed primarily by the deposition of silica from groundwater in cavities of volcanic rocks or sedimentary environments. The botryoidal (grape-like) texture occurs when crystals grow around a central nucleus at a uniform rate.

Uses & applications

Used frequently in lapidary work for making cabochons, as a collector's specimen, and historically for making tools due to its hardness and fracture pattern.

Geological facts

The term 'botryoidal' is derived from the Greek word 'botrys', meaning 'bundle of grapes'. Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen with a standard microscope.

Field identification & locations

Identify in the field by its distinctive 'bumpy' or mounded surface texture, waxy feel, and extreme hardness (will scratch glass). Commonly found in desert regions, riverbeds, and volcanic ash deposits.

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