The Opal, a rainbow of colour play


The Opal is a semi-precious stone and could be divided in different categories. But the best known categories are the dark or black Opal and the white or the light Opal. These opals are opaque with an endless play of colour, fire, also named opalising.
But what causes this effect? Only in the 1960s, when Australian scientists analysed the opal with an electron microscope, they discovered that small spheres from silica gel caused interference and refraction manifestations, which are responsible for the fantastic play of rainbow colours. In the picture here below, a Fire Opal and an Ethiopian Opal, pendant made by jewellery designer Martin Spreng.


They all show in their own special way that unique play of colours. Except the fire Opal, due to its transparency, hasn’t this typical play of colours. The original name of opal was probably derived from Sanskrit “upala”, meaning valuable stone. This was probably the root for the Greek term ‘opallios’, which means colour change. In the days of Roman antiquity there existed a so-called “opalus”, or a stone from several elements. Pliny the Elder, the famous natural philosopher, called the Opal a gem which combines the best possible characteristics of the most beautiful of gemstones: “The fine sparkle of Almandine, the shining purple of Amethyst, the golden yellow of Topaz, and the deep blue of Sapphire so that all colours shine and sparkle together in a beautiful combination“.

Before the 19th century, Opals were relatively rare. In 1849 the first Opal block was accidentally found in Australia, while the prospections started only in 1890 at White Cliff mining.  But the history of Australian Opal began millions of years ago, when parts of Australia were covered by a vast inland sea, and stone sediment was deposited along its shoreline. When the water masses flooded back, they flushed water containing silica into the resulting cavities and niches in the sedimentary rocks, and also the remains of plants and animals were deposited there. Slowly the silica stone transformed into Opal. So from the 19th century, Opals appeared more frequently. During the Art Nouveau period (end of 19th century) jewellery artists even preferred to use opals because of their subdued charm and different aspect. Later during the Art Deco period, the Opal was still a popular gemstone and was often surrounded by enamel or diamonds.
While Australia is now biggest supplier of Fine Opals, other mining countries, as Mexico, Brazil, US, Indonesia, Ethiopia and Mali offer very nice items too.


Text ©World Luxury Jewellers



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