mineral
Opal
Hydrated amorphous silica (SiO2·nH2O)
AI-generated identification · may be incorrectMohs hardness of 5.5-6.5; displays a unique play-of-color; vitreous to resinous luster; amorphous crystal structure lacking a definite crystalline lattice.
Identified More mineral →
Explore Opal in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Mohs hardness of 5.5-6.5; displays a unique play-of-color; vitreous to resinous luster; amorphous crystal structure lacking a definite crystalline lattice.
Formation & geological history
Forms from a solution of silica and water seeping into cracks and voids in sedimentary or volcanic rock over millions of years.
Uses & applications
Primarily used as a gemstone in high-end jewelry, carvings, and collector specimens.
Geological facts
Opal contains up to 20% water trapped within its microscopic silica spheres, which diffract light to create its rainbow effect.
Field identification & locations
Identified easily by its signature play-of-color and lower hardness compared to quartz; mined extensively in Australia and Ethiopia.
More like this
Other mineral specimens
Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Tumbled granite
Granite, a coarse-grained felsic intrusive igneous rock
igneous
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Granite
Granite (Phaneritic intrusive igneous rock)
igneous