About Black Opal – History and Introduction
Black opal is one of the many fascinating varieties of opal available today and it also happens to be one of the most popular varieties. In 2008, Australia officially recognized this and proclaimed black opal to be the official state gemstone for New South Wales. Common opal was already the official gemstone representing all of Australia, because, amazingly, almost all of the world's supply of black opal is mined from New South Wales and an astonishing 97% of all common opal is sourced from Australia.
Black opal is by far the most valuable and appreciated of all opal varieties, especially those from Australia's famous Lightning Ridge. Often, black opal stones will contain aspects of common opal which remain intact throughout production. Typically, common opal is strategically left on the backside of finished black opal stones. The common opal, referred to as 'potch', actually enhances the black opal body tone and accentuates the boisterous vibrancy of other colors that black opal can radiate. It is because of black opal's ability to display such vivid and intense colors that black opal is considered to be the most valuable type of opal available today.
Identifying Black Opal
Black opals can easily be distinguished from common opals by the color of their body tone. However, identifying natural untreated black opal from synthetic, lab created or treated opal can be nearly impossible without proper lab testing and equipment. Typically, if the black opal appears to be too colorful and too perfectly patterned, there is a good chance that it has been enhanced. Natural untreated black opal will typically always have flaws, which make the stone unique.
Black Opal Origin and Gemstone Sources
Almost all black opals are mined from Northern New South Wales and the majority of these are mined specifically from Lightning Ridge. Lighting Ridge has become known as the world's biggest supplier of black opal, and extracts incredible amounts of opal all year round. Other sources for black opal include Ethiopia, but Ethiopian black opal is usually enhanced through smoke treatment to darken the body tone color. No other origin or source can rival the quality and color of Australia's black opal.
Buying Black Opal and Determining Black Opal Gemstone Value
Black Opal Color
Black opal body tones range from a dark gray to black, and the dark background acts as the base for the spectrum of colors it can display. Despite its descriptive name, black opal can, in fact, encompass various colors. Top quality specimens can reflect the full spectrum of colors through their unique play of color quality. Black opal contains subtle traces of iron oxide and carbon elements, which are not found in common opal. These combined elements are responsible for creating the unique traits belonging to black opal. The dark canvas of black opal results in the distinction and reflection of much brighter colors compared to other varieties of opal. Yellow, blue and green are the most common colors seen through play of color, whereas violet, fiery red and orange colors are the most valuable and sought after of opal colors.
Black Opal Clarity and Luster
Black opal clarity is typically translucent to opaque and almost all specimens will have eye visible inclusions such as patches or lines of potch (common opal). With black opal, it is the presence of crazing that can render a specimen worthless. Crazing is due to the drying of opal and it results in surface-reaching cracks or fissures. Black opal should have a wax-like luster, but at the same time, it should not appear to be too 'plasticky'.
Black Opal Cut and Shape
Typically, the shape and cut of a finished black opal will be dependent on the original opal rough. Black opals are most often cut into oval cabochons, but other shapes are also very popular, such as teardrops and trillion shapes. Most black opals are cut with low domes because they have rather thin color bars. If the opal color bar is too thin, it may be unfeasible to fashion any domed surface at all from the stone.
Black Opal Treatment
Australian black opal is typically untreated. Ethiopia is a major source for treated black opal. The treatment used on Ethiopian opal is an old smoking method which allows carbon to deeply penetrate the opal and enhance its color. There have been recently reported enhancements involving a combination of heat and sugar; stones are soaked in a sugar solution and then dipped in sulfuric acid. They are then slowly heated to produce a darker body tone.
Another treatment that has been discovered on some black opal is coating of the gem. This is not as common as heating, but nevertheless, consumers should be aware of this possible enhancement, along with the possibility of impregnation with polymer, resin or oil that is done to stabilize opal.As an eBay seller I am dedicated to making sure every customer walks away feeling as if they received an excellent deal for a high quality item. so please if you have any questions, don hesitate to ask I will respond within 24hrs. Thank You for Shopping at my Store!!!