Andamooka is in the harsh Australian desert and is located 640km by road north of Adelaide, South Australia, near the western margin of Lake Torrens. It was discovered in 1930 and is famous for producing brilliant crystal seam opal. When it reached its peak in the 1960s, the population reached 3,000 and the workings had expanded to an area of 13km by 5km. Up until 1972 Andamooka was a major producer of precious opal with output equaling in value, and sometimes exceeding, that from Coober Pedy.
The types of opal found at Andamooka are:
Seam opal - located on the contact of the conglomerate band and underlying mud. Andamooka can produce some amazing crystal opal, dark opal, light opal, gem opal, white opal, grey opal and milk opal. Usually in a thin seam or level Most opal from Andamooka comes from this opal level as this is generally the best quality.
Andamooka white rough seam opal.
Verticals - opal found filling the voids in verticals above and below the usual opal level and in slides.
Matrix opal – unlike other opal, Andamooka matrix opal is formed within limestone. To the human eye, limestone is a white chalk like substance which causes so much diffraction of the light that we are unable to see the coloured opal held within it. The limestone containing opal does not immediately look like other opal with bright flashes of colour, instead it looks washed out and faint. When the limestone matrix is wet however, the colours can be seen, sometimes the full colour spectrum stands out. Andamooka matrix opal is regularly treated to darken the colour of the host limestone creating a darker host rock, therefore highlighting the sparkles of opal within.
For more technical details on this process see our blog Treating Andamooka matrix opal - with sugar and acid.
Variety of matrix opal sliced ready for shaping and cooking.
Cooked matrix opal ready for shaping and finishing.
Painted Lady – also known as Andamooka boulder opal. The opal develops on joints of quartite boulders, usually as a thin film. These command high prices as specimens.
To see a range of Andamooka opal as finished pieces, please check out our webpage on www.OpalQuest.com
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- Tags: Andamooka, Concrete Opal, Fairy Opal, Matrix, Painted Lady, Rainbow Matrix, Seam Opal, South Australia, White Opal