mineral

Agate (Geode nodule fragment)

Chalcedony (cryptocrystalline variety of Quartz), SiO2

Hardness: 6.5-7 on Mohs scale; Color: Creamy white, grey, and translucent with brown inclusions; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None/Conchoidal fracture; Specific gravity: 2.58-2.64

Hardness: 6
Color: Creamy white, grey, and translucent with brown inclusions
Luster: Waxy to vitreous

Identified April 6, 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 as a secondary deposit in cavities within volcanic or sedimentary rocks. Silica-rich groundwater percolates through voids, depositing layers of chalcedony over thousands to millions of years.

Uses & applications

Commonly used in lapidary work, jewelry (beads, cabochons), metaphysical collecting, and historically for mortar and pestles due to hardness.

Geological facts

Agates often form 'thunder eggs' and are characterized by their concentric banding, though this specimen appears to be a section of a small nodule or geode center with an inclusion or iron staining.

Field identification & locations

Identify in the field by its waxy luster, translucency when held to light, and its ability to scratch glass. Commonly found in riverbeds, desert pavements, and near ancient volcanic sites.

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