Opal, the Birthstone of October.
It is known to be the most magnificent, beautiful and enchanting Gemstone. Majority of the Opal Gemstone is sourced from Australia, making Opal Australia’s State Gemstone.
The appearance of the Opal Gemstone can vary from colourless to white, light grey to black.
Depending from which angle the Gemstone is viewed from the Opal Gemstone shows a variety of bright colours of the spectrum when light passes through the tiny silica spheres in the micro-structure of the Gemstone and the most unique attribute of this Gemstone.
Per Science, the chemical compound of the Opal Gemstone is known as SiO2·nH2O – an amorphous mineraloid comprised of Hydrated Silicon Dioxide, this is a mixture of Silica and Water.
Per the Mythology of Chakra Healing, Opal is a feminine stone that brings hope, enhances feminine energies, sensitivity and female intuition.
It is also said to bring strong energies to your aura, brings calm and relief from emotional stress.
How is the Opal Gemstone Formed?
As you already know the Opal Gemstone is formed from the mixture of Silicon Dioxide and Water.
Water seeps through sandstone and then picks up tiny particles of Silica.
This mixture is then streamed into cracks and voids in sedimentary as well as volcanic areas inland Australia.
Over a period of time approximately between 1 – 2 million years, this mixture solidifies as the climate changed.
The Opal Gemstone therefore remained soft and un-cemented for long periods before becoming hardened hence now it’s a solidified mineral which is used mostly in jewellery making.
Why and How is Opal Coloured?
Once the Silica in the solution is deposited, the water content gradually decreases and the spheres inside forms into a gel.
The spheres are not only remarkably uniform in size but are packed, in gem quality Opal, in a very regular array. Because they are spherical, there are tiny holes remaining in the structure (much the same as when marbles are placed together in a container) and these holes too are arranged in a regular three-dimensional way. Therefore because of the regular array of these cavities, opal is an optical diffraction grating for visible light.
When the spheres are bigger (about 3500 angstroms diameter) the red or orange colours are produced. And at the other end of the scale, at about 1500 angstroms diameter, the blue end of the spectrum is diffracted. Between these figures the rest of the colours of the rainbow occur. From this it can be deduced that the light diffraction in the voids is greatest when the sphere size is greatest.
To summarise, the colours in the Opal Gemstone is caused by the regular array of Silica spheres and voids diffracting white light, and breaking it into the colours of the spectrum.
The diameter and spacing of the spheres controls the colour range of an opal. Small spheres produce the most common Opal Gemstone as they will have a blue colour and as for the rarest Opal Gemstone the spheres will naturally produce the colour red.Therefore, the red is usually the brightest colour and the blue is duller.
The Value of The Opal Gemstone?
This all depends on the uniqueness and the quality of each Opal Gemstone you may have. A lot of factors play a part in this such as the body tone, weight, the blend of colours, the cut of the stone, brilliance, pattern, and size.