mineral

Grey Agate

Silicon Dioxide (SiO2) - Variety of Chalcedony

Hardness: 6.5-7 (Mohs scale); Color: Translucent grey to smoky white; Luster: Waxy to vitreous; Crystal Structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58–2.64

Hardness: 6
Color: Translucent grey to smoky white
Luster: Waxy to vitreous

Identified April 24, 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 scale); Color: Translucent grey to smoky white; Luster: Waxy to vitreous; Crystal Structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58–2.64

Formation & geological history

Formed primarily in volcanic and metamorphic rocks. It occurs as a result of groundwater depositing silica in the hollow cavities or vesicles of igneous rocks. Most specimens date back to the Cretaceous or Tertiary periods.

Uses & applications

Used extensively in jewelry, lapidary arts (tumbled stones), and historically for tool making. Also used for ornamental carvings and as a decorative collector's stone.

Geological facts

Agate is named after the Achates River in Sicily where it was first discovered. Grey agate is often considered an 'earthy' stone associated with grounding and stability in metaphysical circles.

Field identification & locations

Identify in the field by its waxy luster, conchoidal fracture, and translucency. It is often found as nodules in stream beds or coastal areas where volcanic rock has weathered away.

Other mineral specimens

See all

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