Opal: Mineral information, data and localities.

Although it is still (2007) regarded as a mineral species for historical reasons, opal is not a true mineral in the accepted sense of the word as it is

Opal-A: Mineral information, data and localities.

Rare $675,000 opal makes public debut

Opal - Wikipedia

Minerals, Free Full-Text

Polished Dendritic White Opal Hearts x 8 From Moralambo, Madagascar

Opal: The mineral Opal (black, white, fire) information and pictures

Boulder opal

Yellow Opal (rare locality) Opal occurrence, Cercle de Nioro du Sahel, Kayes Region, Mali

File:Precious opal (Berbere Hill, Ethiopia) 20.jpg - Wikipedia

Opal : Properties, Formation, Uses and Deposits » Geology Science

Polished Complex Wispy Green Opal Standing Free Forms x 3 From Antsirabe, Madagascar

Opal - Wikipedia

Milk Opal: Mineral information, data and localities.