Mineral Factbook

Opal

SiO2·nH2OIMA symbol: Oplgrandfathered

Opal is an oxide or hydroxide mineral with the formula SiO2·nH2O, crystallizing in the amorphous solid system. Its streak is white.

Photos

Opal specimen photo
Guilhem Vellut from Annecy, France · CC BY 2.0 · Commons
Opal specimen photo
Osama Shukir Muhammed Amin FRCP(Glasg) · CC BY-SA 4.0 · Commons
Opal specimen photo
Eunostos · CC BY-SA 4.0 · Commons
Opal specimen photo
Maatpublishing · CC BY 4.0 · Commons

Physical properties

Streak
whitesingle sourceWikidata (CC0)

Classification

Nickel-Strunz (10th)4.DA.10Wikidata (CC0)
Nickel-Strunz (9th)4.DA.10Wikidata (CC0)
Dana (8th)75.2.1.1Wikidata (CC0)