Stone of many colours

Opals are commonly pictured as translucent, pale, grey-green stones flecked with ghostly colours. In fact, they come in several bright colours and are especially prized by Librans.

Known since antiquity, the opal gets its name from the Roman word opalus, a Latin version of the Sanskrit upala, meaning “precious stone”. Opal is hardened silica gel and usually contains five to ten percent water in submicroscopic pores. Precious opal is the least crystalline form of the mineral, consisting of a regular arrangement of tiny, transparent silica spheres with water in the intervening spaces.

OpalOpal is deposited at low temperatures from silicon-bearing water. It is commonly found as fossilized wood, where it preserves the wood’s external appearance and cellular structure. Precious opals can form only in undisturbed space within another rock that is capable of holding a clean solution of silica from which water is slowly removed over a long period – perhaps thousands of years.

An early description of opal appears in Pliny the Elder’s treatise titled Naturalis Historia (Natural History) published about AD 77-79. In Book XXXVII Pliny says:

“Made up of the glories of the most precious gems, to describe opals is a matter of inexpressible difficulty. For there is among them the gentler fire of the ruby, there is the rich purple of the amethyst, there is the sea-green of the emerald, and all shining together in an indescribable union. Others, by an excessive heightening of their hues, equal all the colours of the painter, others the flame of burning brimstone, or of a fire quickened by oil.”

Opals were prized for their beauty and supernatural powers. In 1597, Queen Elizabeth I of England gave her favourite buccaneer, Sir Francis Drake, an expensive brooch for his cap: a ruby carved with an orb and cross surrounded by eight fine opals and the whole rimmed by alternating diamonds and opals.

Feste, the clown in Shakespeare’s play Twelfth Night, written around 1601, says to Duke Orsino, “Now, the melancholy god protect thee, and the tailor make thy doublet of changeable taffeta, for thy mind is a very opal.” The use of “taffeta” and “opal” refers to the effect of light on both the material and the stone: fickleness, inconstancy, mutability. Shakespeare must have seen opals at Queen Elizabeth’s court.

Two centuries later, following the publication of Sir Walter Scott’s Anne of Geierstein, or The Maiden of the Mist (1829), the opal began to lose its auspicious reputation. In Scott’s novel, the Lady Hermione wears a dazzling opal with magical. But when a drop of holy water falls on the talisman, the opal turns into a colourless stone and the day afterwards Hermione turns to ashes. Such was the popularity of Scott’s novel that people began to associate opals with bad luck and death.

Black-opalFire-opalUntil late in the 19th century, the primary source of precious opals, including those used by the Romans, was in present-day Slovakia. Today, the chief producer is Australia, where it was discovered in 1887. The Lightning Ridge field in New South Wales is the source of the prized black opal (left), with its very dark grey or blue to black body-colour. Until the discovery of this field in 1903, black opal was virtually unknown and it is still the rarest form of the gem. Another form is called the fire opal (right). This transparent, intensely coloured opal in red, orange or yellow comes mainly from Mexico and Honduras.

In Aboriginal mythology, it was the rainbow that created the opal’s many colours. In August 1956 the world’s largest and most valuable gem opal, the “Olympic Australis”, was found at the “Eight Mile” field in Coober Pedy, South Australia, weighing 17,000 carats (3,450 g). And on 27 July 1993 the opal became Australia’s national gem stone.

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