Opal is a hydrated silica which consists of spherical particles which have settled in a regularly stacked pattern to reflect light back in different colours. This is what is called a ‘play of colour’. Opal is not in it self a coloured gem, it only reflects colour back when hit by a light source.

The smaller spheres reflect the blue colours back, medium size spheres the green, the largest spheres reflect back red colour.

In Australia the most common opal is the light opal which is found in Coober Pedy, Andamooka and White Cliffs. Boulder opal is found in Queensland. This is opal which has settled in veins in ironstone boulders.

In Lightning Ridge and surrounding areas, a wide range of opals are found. Crystal, light dark and black opals, from low grade to extremely high quality.

This is just a short description of opals to give you a quick run down.

You can read more about opals on the following site. It’s a NSW government site which gives good description about opal and also has the full opal classification, which explains the difference between the different kinds of opals;

http://www.dpi.nsw.gov.au/