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

Apatite: Mineral information, data, localities and healing benefits

Opal / (variety - “Opal-AN”) / (variety - “Hyalite Opal”) / (“Blood Vessel Opal”) / Locality - San Luis Potosi, Mexico

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

Opal - Wikipedia

What Is Opal - Gemstone Facts and Information

Opal gemstone information

Rare $675,000 opal makes public debut

Wax Opal: Mineral information, data and localities.

Opal, Properties, Types & Uses

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

Opal-An (hyalite opal) from Zacatecas, Mexico. (A) Natural light. (B)

Milk Opal: Mineral information, data and localities.

Opal Mineral Information photos and Facts, Manganese Ore

Opal, Properties, Types & Uses