WHAT IS AN OPAL?
According to Aboriginal legend:
Their ancestor conveyed himself to earth by a great rainbow,
where the rainbow rested there was now a great area of rocks with
all the colours of the rainbow - these were the first Opals.
65 Million Years Ago at the end of the Cretaceous period sea levels receded and the vast desert sandstones were laid down, 30 Million Years Ago – during the mid-Tertiary period Opalisation began.
50,000 Years Ago - Australian Aboriginal 'dreamtime' regards the birth of Opal as sacred.
1840 - First discovery of Australian Opal at Angaston, South Australia.
1912 - Opal proclaimed October birthstone by American National Association of Jewelers.
Precious opal is unique, no two opals are exactly the same. The colours and patterns are always changing, making the opal a gem of infinite beauty. Opal can display all the colours of the spectrum due to the interference and diffraction of light passing through the tiny silica spheres in the structure of the Opal.
Opal is defined as a hydrated form of silica (Si O2,n H2O).
Australia produces over 90% of the world’s supply of precious Opal and 100% of the highest quality gems.
Precious Opal is classified on the basis ofthe background colour and the type of colour pattern.
Black Opal shows a play of spectral colours in a dark body
Light, Fire or Crystal Opal has a body colour ranging from milky white to translucent.
Boulder Opal is light or dark Opal found in veins of ironstone.
Many factors must be considered when valuing opal, the intensity or brilliance of color is of most importance, the finest of opals are of maximum brightness and clarity. There should be an even play of color all over the stone. The stones should be free from obvious flaws on the face of the opal but marks on the base do not affect the value.