The Introduction to Opal
Opal is primarily made up from a variety of natural silica found in the earth. Over very long periods of time the silica is mixed with water (rain) and is deposited in cracks and holes in the earth, hardens and becomes opal.
The worldwide opal industry relies heavily on Australia for its supply. A massive 95% of opal used for jewellery purposes is found in Australia. A small number of other countries including Mexico, brazil and the USA do produce some opal but it is inferior and simply does not have the appeal and instant recognition that Australian opal holds.
Although this is one of the most effective ways of finding opal, it is also the most laborious. The length of the shaft could be as short as three metres or as long as 20 metres. A drilling rig with a 36-inch bucket auger would save a miner the several days it could take several days to reach the opal level by hand.
A variety of miner’s tools are needed, including a hand windlass or motorised winch that is placed over the hole to lift dirt to the surface; or an expensive vacuum-cleaner apparatus, called a ‘blower’. The working pattern changes once the ‘bottom’ of the shaft has been reach, that is, where the opal-bearing dirt begins. Now the miner begins gouging away very slowly and carefully, forming a horizontal tunnel in the hope of finding a tiny seam of precious opal, or scattered ‘nobbies’ as at Lightning Ridge.
Opals Cutting and Polishing
Once the opals are mined they will be cut and polished by experts to remove any remaining dirt and opal potch that is still attached and reveal the true colours and patterns that exist in each individual stone.
Almost all opals are cut in the cabochon form and due to the nature of opal they generally will be cut in freeform shape so as to maximise the potential in size and colours that may be present in the stone.
Grinding Mill to satisfy the Opal Mining
On the basis of the traditional grinder, Straight Centrifugal Grinding mill are designed to grind thick powder to meet the requirements of the customer. And it has fulfilled the customer for the mixed materials of thin degree with the finished product below 3mm. The amount of the energy consumption which the Straight Centrifugal grinder’s blower consuming is only 6% of mill, but Raymond mill is 81% .In addition, the consumed energy when the spiller slides the stone occupies 25% of the whole energy ,but straight centrifugal grinder has no such consumption.