Thursday, August 26, 2010

⤱ Opal ⤱

Opal is an amorphous form of silica with a formula of SiO2.nH2O. Opal without 'fire' is usually referred to as potch. Colourless opal that forms as spheres is known as hyalite, and this form is often fluorescent under UV light. The form that has 'fire' or a play of colour is known as precious opal.

This specimen is boulder opal (Yowah Nut) from Yowah, Queensland.