sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness: 6.5 to 7 on the Mohs scale. Color: Brown, translucent with bands of various shades. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline quartz). Cleavage: None (exhibits conchoidal fracture). Specific gravity: 2.60 to 2.65.
- Hardness
- 6
- Color
- Brown, translucent with bands of various shades
- Luster
- Waxy to vitreous
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: 6.5 to 7 on the Mohs scale. Color: Brown, translucent with bands of various shades. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline quartz). Cleavage: None (exhibits conchoidal fracture). Specific gravity: 2.60 to 2.65.
Formation & geological history
Forms primarily within cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater in concentric layers over millions of years.
Uses & applications
Used in ornamental objects, jewelry, polished specimens, decorative carvings, and previously for precision instrument bearings and mortars.
Geological facts
Agate is one of the most popular and varied stones used in lapidary arts. The ancient Greeks and Romans prized it for its medicinal and protective properties.
Field identification & locations
Identified by its waxy luster, hardness (scratches glass), conchoidal fracture, and often translucent banded patterns. Commonly found in river gravels, volcanic regions, and geodes 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