1 - Country of origin and the mine the material was dug from
2 - The dimensions of the opal in mm or the average size if rough pieces
3 - The weight of the item in carats (5 carats = 1 Gram, 31 grams = 1 Troy Oz, 1000 grams = 1 kilo)
4 - The colour of the Opals Body Tone N1 - N4 - Is for black tone body types. Body Tone N5 - N9 - Is for lighter coloured Opals.
5 - The colour of the precious opal produces when in a direct bright light source, this can change from sunlight to artificial light.
6 - How bright the fire colour is to the eye, from 5 being the brightest down to 1 being the dullest. These are graded like 4 out of 5 eg 4/5.
Opal will arrive in a clear sealed plastic wallet, please view the opal in the wallet removing the opal will mean you can not return the item as it will be classed as touched/altered. There is a tamper seal sticker please leave in place to return opal.
Delivery times in the UK are normally around 3-5 works days - All orders are sent tracked unless stated otherwise.
International orders are 7-21 working days (hold ups in customs may make this longer until you have paid your import duty)
Opal formation
The local name given potch, such as desert sandstone, is dependent upon the area in which they occur, but they all belong to the same families of felspathic sandstone, claystone, siltstone and mudstone, which are said to have been deposited over large areas buy streams and lakes.
We call any material that opal colour has formed on as Potch. Except for volcanic opal, which usually occurs in Tertiary rocks, all the types of opal we have come to know so well are found in these strata. Although the opal is found in the Cretaceous sediments, it is a matter of conjecture as to its deposition over millions of years during the Tertiary period. The general teaching is that certain minerals were broken down in the country rock to produce silica at 120 parts per million, and trace elements which were deposited in cavities left by bones, shells and other dissoluble material. These, as well as faults and fractures in the ground, provided pathways for the underground waters to carry the silica down at the end of the weathering period.
Although this is the entrenched theory, with ?slight variations? depending on your source of information, it is fraught with problems which have been deleted from the model to give it credence. There is little doubt that all opal was not deposited in exactly the same manner. So far I have discovered four different ways in which it has been deposited; there may be more. They all have a common denominator in the equation, ionic-exchange. The fact is that opalization is extremely regional and that large beds of impervious barriers are only secondary to opal formation.
If the only requisite for opalization under the above model were suitable impervious traps, then there would be massive beds of opal over vast areas. However, as every opal miner knows, this is not the case and all opal is unpredictable and patchy in the extreme.
Australian Opal is rarely faceted, nearly always domed. A domed stone is stronger and less prone to chipping. However Opal without a play of colour (such as cherry red or amber Opal from Mexico) is often faceted and can look a lot like ruby. Opals are a carvers delight. The stone is not too hard to work with and will not wear out your diamond tools as much as such stones as Chrysoprase and Agate.