But we do know that the sapphires which are found today were formed around to million years ago. Today the modern location of rubies and sapphires gives us some clues and indications about the place of their formation.
The main deposits of high quality sapphires and rubies are found only in a few places, mainly southern Asia and eastern Africa and the islands of Sri Lanka Ceylon and Madagascar.
The answer as to what took place inside the earth to form these gems and then transport them to the surface varies from country to country, but the story remains the same. Later the moving crustal plates and erupting volcanoes carried these rocks to the surface.
Sapphires have been found in many other places in the world but few have attained the desirability of the Kashmir stones. In the United States, the Yogo Gulch area in Montana has historically produced some fine sapphires but few of these attain the size of the fine Kashmir gems. Labor and mining costs have been very high in the United States and the Yogo Gulch mines have generally not been profitable for the operators.
Fee localities are areas where one can pay a set fee for the privilege to extract gems and minerals from mines or claims that are owned by a second party. There are several such fee locality sapphire mines in Montana that have been profitable for both the mine owners and the prospectors who have chosen to pay the fee.
The prospector pays a set fee for the right to extract a given weight or volume of sapphire bearing rock or gravel. The fee locality operators allow only the use of hand tools such as picks, shovels, crowbars, gads and wedges. The miner extracts the sapphire bearing rock with the larger tools. This material is sieved through a series of screens that allow the miner to separate and discard the extremely large cobbles as well as the very fine grained sand, silt and clay.
The volume the miner pays for is actually only that that is in the size range that will produce the most useable stones. The sieved residue is placed in buckets and toward the end of the day the miners return to the base camp where the operators have electric shake tables that wash the gravel and concentrate the particles with high specific gravity toward the bottom of a pan.
A half-ton of gravel may actually yield only a few pounds of sapphire bearing concentrate. When the concentrate is collected in the pan, the pan is removed from the shaker and is dumped over quickly on a flat table. The largest sapphires will normally be on the top of the pile or what was earlier the bottom of the pan.
Smaller stones may be found through the rest of the concentrate. In addition to sapphire being found in Montana, some stones have also been produced from mines in North Carolina where several fee localities exist. Ruby deposits are more uncommon as they depend on the presence of the rare element chromium.
Ruby is usually found in metamorphic rocks, such as those in the Harts Range in the Northern Territory. However, a more transparent, gemstone-quality ruby comes from a few areas in eastern Australia where it has been brought up from underlying metamorphic rocks by volcanic action. Marc Antoine Gaudin synthesised the first rubies by fusing alumina with chromium in Ten years later Jacques- Joseph Ebelmen made artificial sapphires by fusing alumina with boric acid.
Auguste Verneuil developed a process for producing large flawless sapphires and rubies in These crystals have many industrial uses including as mechanical bearings, as laser components, and in optics. Sapphires and rubies have been found in all eastern Australian states, including Tasmania. The Kings Plains area, near Inverell, has some of the richest deposits of gem-quality sapphires ever mined.
In addition, sapphires have been recovered from old tin workings along the Weld River in Tasmania. There are many sites where fossickers can try and find sapphires and rubies in these regions too.
The most significant occurrence of ruby is near Gloucester, near Mount Barrington, an old volcano. Rubies have also been found in the vicinity of the Macquarie and Cudgegong Rivers and near Tumbarumba. See map.
Currently commercial mining of corundum including sapphire and ruby still occurs at the Anakie and Lava Plains placer deposits in Queensland, and the New England area of New South Wales. Open pit mining is used to extract the corundum ore from the gravels.
In many cases the mining operations are small and the pits quite shallow. Tools used might include jack hammers, excavators or shovels. Some countries in Africa and South America use high water pressure mining to produce large quantities of rough corundum gems. However, many gem buyers boycott companies using this practice, because this method strips away all the top soil destroying the local environment. Once mined, corundum can be separated from clay and gravel because it is more dense and heavy.
Usually, the gravel is broken up and sorted into size fractions in a rotating drum trammel , and then washed either by hand or with a high pressure water jet, over filters with various size holes.
The heavy grains will sink and the lighter materials, like clay, will wash over the top. The remaining material also contains other heavy minerals such as magnetite and zircon. Magnets can be used to get rid of magnetic material and then zircons are removed by hand. The corundum is then visually assessed and graded according to size and colour. Sapphires and rubies can be artificially altered to improve their value or appearance.
Heat and irradiation can enhance the colour intensity as well as the clarity of the gemstones. Red corundum is referred to as a ruby. During the formation of corundum, the coloring of the stone is dependent upon what minerals are present. For instance, when iron is present, sapphires may have a green or yellow hue to them, whereas the presence of vanadium will create purple sapphires.
The most prized sapphires are blue, which is a result of titanium being present when the stone is formed. With advances in science and technology, methods have been created for artificially growing sapphire crystals. The original process was discovered in , and it consisted of alumina powder being added to a oxyhydrogen flame, which is in turn directed downward. Alumina in this flame is slowly "deposited" in a teardrop shape called a boule. A variety of chemicals can be added throughout this process to create sapphires of multiple hues, as well as red rubies.
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