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

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

Polished Green Opal Standing Free Form x 12 From Antsirabe, Madagascar

Rare $675,000 opal makes public debut

Apatite: Mineral information, data, localities and healing benefits

Opal - Wikipedia

Opal Geoscience Australia

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

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

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

Opal-AG: Mineral information, data and localities.