sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, colors range from white, grey, blue, green, red, to brown, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture with no cleavage, specific gravity of 2.58 to 2.64.
Identified More sedimentary →
Explore Agate in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 6.5 to 7 on the Mohs scale, colors range from white, grey, blue, green, red, to brown, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture with no cleavage, specific gravity of 2.58 to 2.64.
Formation & geological history
Formed primarily within metamorphic and igneous rocks, most commonly as nodules in volcanic rocks (such as basalts) through the deposition of silica from groundwater in cavities over geological time.
Uses & applications
Used extensively for ornamental objects, jewelry, tumbled stones, decorative carvings, and precision instruments like mortars and pestles due to its durability.
Geological facts
Agates are named after the Achates River in Sicily, where stones were found in antiquity. They often form in concentric bands corresponding to different stages of silica deposition.
Field identification & locations
Can be identified in the field by its waxy luster, conchoidal fracture, and characteristic banding patterns. Commonly found in stream beds, gravel deposits, and volcanic regions worldwide.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary