Since 1970 I have cut and treated thousands of carats of
Andamooka opal of all types. I lived just 80 miles from the mines
for 4 years.
For everyones clarification, not all Andamooka opals are of the
treatable “matrix” variety. In fact, only a small percentage of
the Andamooka production is of this variety. Most is nice milky
white based with poor to great fire, green crystal, jelly, or gem
crystal variety with a rare black thrown in now and then
Also, only a very small percentage of the treatable matrix
variety is truly “oolitic”. Most of it is sandstone or clay, with
precious opal saturating the majority of the pore spaces between
the sand or clay particles. There is enough penetrable space left
for the sugar to be deposited and react with the sulpheric acid,
leaving the pure black carbon behind.
This treatment usually penetrates about 1mm into the stone.
Re-cutting can remove part or all of the treatment, and you have
already read the method for restoration.
Enjoy your opals!
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Bangkok 10500 Thailand
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