Image: <bdi><a href="https://www.wikidata.org/wiki/Q126871368" class="extiw" title="d:Q126871368"><span title="photographer from the United States">Darla Sondrol</span></a></bdi> (CC0)
amorphousuncommonMineraloid (hydrated amorphous silica)
Opal
SiO2·nH2O
This image displays a polished opal cabochon, likely white or light-bodied, showcasing the characteristic iridescent play-of-color that shifts with viewing angle.
Opal Physical Properties
Mohs Hardness
5.5Crystal System
amorphousLuster
vitreousStreak Color
whiteCleavage
noneFracture
conchoidalSpecific Gravity
2.1Colors
white, black, gray, yellow, orange, red, green, blue, pink, colorless, with play-of-colorTransparency
transparentType Locality
variousMineral Group
Mineraloid (hydrated amorphous silica)Uses
jewelry, collectorAssociated Minerals
chalcedony, quartz, limonite, sandstone, basaltRarity
uncommonGeological Context
Opal forms from the deposition of silica-rich waters at low temperatures, often filling cavities in sedimentary or volcanic rocks. The water content can indicate the temperature of the host rock during its formation.
