The Name Opal derived its name from the Sanskrit word Upala meaning Jewel and Latin Opalus meaning to see a change in color. The ancient Romans spread the word about Opals more than two thousand years ago. Opals at the time, Romans being led to believe to have come from India, were said to have actually been found in a province of the then Hungry (Modern day Slovakia). In 1889 a new source of Opal was found in Far off Australia. Producing the finest opal the world had ever seen. Currently it is said that Australia produces 95% of the worlds Opal supply.
Opal has been used in crowns of Kings and Queens. Romans coveted the precious stones. An amazing Opal called Burning of Troy which displayed striking Red Flashes was a gift to Josephine from Napoleon. Queen Victoria became a lover of opal and wore them throughout her reign. Opals gained in popularity world-wide due to the Royal Court of England, as they were considered the model of fashion around the world. Some of the world's most notable designers like Tiffany, Lalique and Cartier used Opal extensively.
Throughout history Opals have been regarded as the stone of good health and fortune. There can be no doubt that much of the modern superstition regarding the supposed unlucky quality of the opal owes its origin to the misreading of Anne of Geierstein, (The Maiden of the Mist), Sir Walter Scott's Novel from 1829. The wonderful tale contains nothing to indicate that Scott really meant it to represent opal as unlucky, being blamed for a death. However it seems the myth stems back to the middle ages. Shakespeare was attributed with the description of opal as "that miracle and queen of gems." Today in a number of cultures, opal is carried or wore as a good luck talisman - the stone of hope and good fortune.
Black Opal is a generic term given to any Opal which has a dark body color. Some have a transparent crystal color bar overlaying dark Opal Potch giving the otherwise light Opal a dark appearance . Even expensive black Opals may have only a thin color bar on black Potch. Black Opals are the rarest and most valuable.
Boulder Opal is a variety of precious Opal that forms naturally within the host rock: often just a thin vein of precious Opal is present. It mainly occurs in specific location over a wide area of western Queensland Australia. Forming as the in-filling of cracks or voids usually in ironstone boulder. Boulder Opal can be black or light depending on the appearance when viewing from the face of the Opal. Fine Boulder opal grade has the top surface covered with precious Opal. Slight marks and protrusions of Ironstone in the face of the stone are fairly typical and can affect the stone's value. The most expensive Opal are those with dark body tones and display a full face of the precious Opal. Boulder matrix or picture boulder has veins or patches of precious Opal intimately mixed with the host rock and create beautiful natural abstracts in the boulder ironstone.
Light opal is commonly referred to as "white", although this term should only be used when the body color is milky or white. It should not be used to describe the entire light Opal family. Light Opal makes up the bulk of precious Opal and comes from all the fields, but the majority are found in South Australia. Brilliant light Opal can be extremely valuable. The transparent material (crystal) variety commands the highest prices.
Composite opal comprises of natural Opal mechanically attached to another substance. Triplets and Doublets are a combination of natural Opals, artificially attached veneers. It is important not to submerse composite Opals in water, chemicals or detergents, as this can cause deterioration of the glues and cements causing delamination of the veneers.
Precious Opal is composed of minute uniform spheres of silica which are arranged together in an orderly three dimensional grid. The spaces between the spheres contain silica in solution. However in common Opal where there is a play of color, the spheres are varying in size and not uniformly stacked.
The color of opal is dependent on the size of the sphere which intern determines the wavelength of light diffracted. For instance, blue colors are evident where spheres are smaller. At the other end of the spectrum, orange and red are evident where the spheres are longer.
Intensity and brilliance of color are a result of the degree of uniformity of the size and regularity of the grids.
Unprecedented demand over the last two decades and the shortening of supply for fine opal has caused Opal values to soar. The cost of fine quality Black Opal rivals those of diamonds.
Brilliance is of paramount importance. A gem that glows but is average in all other respects will still command a high price. Whereas a dull stone even with a very good pattern and range of color may command only average prices.
Light opal is more desirable when it has a degree of transparency and if lively brilliant colors are present in the crystal, thus commanding a higher price.
The majority of Opal is quite hard and will scratch glass. However there are a few areas at some fields that produce unstable Opal, which can crack or craze. It is important to source your Opals from reputable traders whom guarantee their stone's quality.
Solid Australian Opal has a hardness of 6 to 7 on the Mohs hardness scale (. For reference: Pearl is 3.5, Glass is 5, Tanzanite is 6.5, Emerald is 7.75, Sapphire is 9, and Diamond being the hardest at 10.
Opal is quite resilient, but (as is the case with any valuable jewelry and precious stones) care should be taken to avoid situations where the Opal will come in contact with abrasives or be subject to impact. Opals should be worn and enjoyed by everyone. As Plinky the Elder wrote "For in them you shall see the living fire of Ruby, the glorious purple of the Amethyst, the sea-green of the Emerald, all glittering together in an incredible mixture of light". (Pliny Ist Century AD)