Opal: The Birthstone of October

The spectacular kaleidoscopic colours of opals are unlike any other gemstone. This unique gemstone is the birthstone for colourful characters born in October.

Opals are famous for their breathtaking interaction with light, creating a mystical aura that has the power to stir the imagination. As light dances across the surface of opal gemstones, imagery of fireworks, neon signs and far away galaxies come to mind.

The incredibly diverse opal can come in combinations of almost every colour of the rainbow, from bluey greens to intense reds and oranges. Opals can occur in a variety of different surface patterns including pinfire, dragon skin pattern, Chinese writing pattern, harlequin and a rolling flash pattern.

Opals are composed of hydrated silica. Opals found in Central Australian towns such as Coober Pedy were formed over a process lasting hundreds of millions of years. The Eromanga Sea which once flooded the Great Artesian Basin retreated, increasing the acidity of the water as the centre of Australia slowly dried out. Silica in surrounding sandstone was released as a result of the chemical weathering, causing a silica-rich gel to fill crevices in nearby rocks. As water evaporates from the rocks, the silica is deposited as tiny spheres which make up opal gemstones.

Opal deposits in Australia make up a huge 95% of the world’s supply. The incredible similarities between the landscape of the red centre of Australia and Mars reveal why opals are also found below the surface of the red planet.

Famous opals include the Aurora Australis which was mined from Lightning Ridge, NSW in 1938. Valued at $1 million, the harlequin patterned opal is named after the beautiful Southern Lights seen in the Australian night sky.

Aurora Australis
Figure 1. Aurora Australis discovered in Lightning Ridge, NSW in 1938.

Numerous prominent figures have been known to wear opal jewellery, including Queen Elizabeth II, Cleopatra, Elizabeth Taylor, Blake Lively, Elvis Presley and Victoir de Castellane (Creative Director of Christian Dior’s).

Watch
Figure 2. Timepiece from the Dior et d’Opales collection designed by Victoire de Castellane.

During the middle Ages, people marveled the chameleon-like colours of opals, believing that opal possessed the virtues of each gemstone whose colour appeared on the surface. Nowadays, opal fortune has turned, as they are considered to be unlucky when worn by those not born in October. This superstition arose following the novel Anne of Geierstein written by Sir Walton Scott where a character is reduced to mere ashes hours after a drop of holy water landed on her opal hair clasp turning into a colourless common pebble.

Despite the negative press received by opals, they are still considered to be a symbol of hope, innocence and purity. As the traditional gemstone of the 14th wedding anniversary, it is also associated with fidelity. When worn by an unfaithful partner, it is said that an opal will lose its luster.