Gemstones: Opal

All of Nature’s splendor is reflected in the opulence of fine Opals: fire and brilliance of all the colors of the rainbow. Australia is the country most associated with Opals origin. Almost 95% of all fine Opals come from the dry and remote Australian Outback deserts.

The family of Opals can include quite a number of wonderful gemstones, which share one characteristic: they show a wonderful dance of colors, which is called “Opalising”. Depending on the kind, place of occurrence, and color of the main body, we differentiate Black Opal, White Opal, Crystal Opal, Boulder Opal, Opal Matrix, Mexican and Fire Opal and Blue Opal. Opal variations are practically unlimited and all show their own dance of colors. Fire Opal, which due to its transparency, doesn't have a dance of color but is nevertheless considered a Fine Opal while other Opals that are lacking the typical play of colors are named “Common Opal”.

Opals were relatively overlooked until the mid the 19th century. But then their career boomed suddenly because contemporary gemstone artists started preferring them to all other stones because of their colorful charm, which in turn was excellently suited to be combined with enamel, another very popular material of those days.

Opal’s color play emanates a very special attraction and fascination. Opals play of color is caused by small spheres from silica gel caused interference and refraction manifestations. The spheres, which are arranged in more or less compact structures, succeed in dissecting the light on its passage through the gemstone and turning it into all the colors of the rainbow.

Australia is the classical Opal country and today is the worldwide most important supplier of Fine Opals. Almost 95 per cent of all Opals come from Australian mines. The remaining five per cent are mined in Mexico, and in Brazil’s north, also in the US states of Idaho and Nevada, but recently the stones have also been found in Ethiopia and in the West African country of Mali.

In 1849 the first Opal blocks were accidentally found on an Australian cattle station called Tarravilla .

The most popular location is probably Lightning Ridge in Australia where most coveted Black Opal is found.

The largest Opal found, 6 ,843 kilograms, named “Andamooka Desert Flame”.

Opal prospectors made their home in deep holes or caves in the ground so they can protect themselves from the burning heat of daytime and from the icy winds of night time. They usually they worked only with tools such as pick and shovel. Buckets full of soil, hopefully containing Opal rocks, were pulled up out of the depths of 5 to 40 m deep shafts by hand.

Being an Opal prospector is still not an easy job even with modern technical tools available.

In order to best bring out the beautiful play of color in an Opal, the stones are cut and polished into cabochons. Only the best qualities of Fire Opal are suited to faceting. The Opal cutter will first of all carefully remove any impurities using a diamond cutting wheel, before working out the rough basic shape. Then comes the fine cutting, the finishing with sandpaper and then the final polishing with a wet leather wheel.

Opal is often found as flat lenses, or thin layers while bigger pieces are very rare. If you leave a thin layer of the harder mother rock, you will have the Opals that are frequently used today for mass produced jewelry. Gemstone combinations consisting of a surface from millimeter-thin Opal plates and have been mounted on Onyx or Black Obsidian and then receives an additional cover from Rock Crystal, Plastic, Hard Glass or Lead Glass for protection.

Opals are a gel made from silica with varying percentages of water. Due to the differing percentage of water, Opals can become brittle. Thus if stored too dry or exposed to heat over a longer period of time, Opals will show fissures and the play of color will become paler. Therefore, Opal jewelry should be worn as much as possible so the Opal will receive the much needed humidity from the air and from the skin of its wearer. Dabbing a damp cloth on the Opal also won't hurt your Opal.

Opals are not very hard and only achieve 5.5 to 6 on the Mohs’ scale. Because they are soft, Opals should be in a protective setting and away from many activities.

In earlier days the Opal’s soft surface was often oiled, but today also sealing them with colorless artificial resin has become quite popular.

Opal’s value is not only determined by the body color or it's transparency but based on place of the occurrence and it's pattern. It is also important if the stone is transparent, translucent or opaque because the Opalizing effect may also influence the transparency. If red appears when looking through the stone then all the other colors will appear. For evaluating Opals the thickness of the Opal layer is considered, the beauty of the patterning, the cut, weight and finish.

Black Opal shows the most brilliant play of colors while runner up Crystal Opal, is transparent with a deep play of colors. White Opals show more diffuse colors and are the least expensive Opals.