October’s birthstone is the highly individual Opal- from the Greek Opallos meaning to see a change of colour. Opalescence is the ability of a stone to scatter and disperse light which affects the colour we perceive. The Romans prized Opal above all other gems because of its fiery play of colour which they felt was a very mysterious almost magical property.
Unlike most gemstones which have a crystalline formation; Opal forms as an amorphous substance – deposits accumulate layer upon layer. Opal is largely composed of Silica and occurs in host rocks such as sandstone and ironstone.
Highly coloured and valuable opals are produced in Australia with distinct varieties specific to different regions such as S. Australia where top quality precious light opals are mined in hot dry zones such as Coober Pedy and Andamooka. These are characterized by their light often creamy body tone and can occur with very attractive pink/peachy tones.
In New South Wales the rare and highly prized black opals are found which have a darker body tone – often a deep blue.
Tropical Queensland is known for its vivid blue/green ‘boulder opals’ – usually cut as ‘freeforms’ : a rough oval or pear shape often with a slice of the host rock (Ironstone) visible to the base. Boulders are also regularly seen as ‘composite’ stones – doublets or triplets which effectively have a natural gem veneer adhered to a base of other material, distinguishable by a perfectly straight juncture
In recent times Hydrophane or ‘Water Opals’ from Welo in Ethiopia are appearing on the market – bright vivid gems often fashioned into cabochons or ‘rondelles’ for beads -truly lovely gems with an appealing translucency.
Any superstitions associated with Opal are due entirely to a work of fiction by Sir Walter Scott and should not prevent you from taking a closer look at these beautiful gemstones. Be aware however that there is a great amount of reconstituted or synthetic opal available on the market today; if in doubt; come and talk to one of our expert salesteam.