Opal, my absolute favourite gemstone, is a gem-quality form of hydrated amorphous silicon dioxide. The name Opal was probably derived either from the Sanskrit word "upala" meaning "valuable stone", or from the Greek work "opallus" which means to see a change in color.
Precious opal is known for its remarkable ability to diffract light, which results in rainbow-like colours that change with the angle of observation - known as 'play of colour'. This colour in precious opal 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 opal of blue colour only (the most common), whereas larger spheres produce red (the rarest colour).
Fire opal can sometimes exhibit slight colour play, but it is better known for its vivid body colour. Common opal is usually opaque, rarely translucent, and lacks play of colour.
Approximately 95% of the world's precious opal comes from Australia, and opal is Australia's national gemstone. The remaining 5% are mined in Mexico, in Brazil's north, in the US states of Idaho and Nevada, and more recently in Ethiopia and Mali.
According to an old Australian Aboriginal legend, the Creator came down from the heavens on a rainbow and delivered a message of peace for all mankind. Stones that were near the place where His feet touched the ground suddenly came to life and began to sparkle. This was believed to be the birth of opal.
Pictured above is my Boulder Opal and Sterling Silver Necklace.
Below are some more examples of Opal Jewellery from members of the Jewellery on Etsy team.