[Jewelry making - Article 00346] - Re: [Orchid] Andamooka opal

[Erich Sommer]

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Dear David

    Methinks you might have been a little misinformed. Andamooka is the
    name of an opal mining town in South Australia, the area around
    which produces some very fine opal indeed with much "play of
    colour". This opal is sometimes found in a matrix of pale creamy
    colour which when treated may show up some lovely colours lurking
    there. 

    The treatment method consists of soaking in a sugar solution and
    then a sulphuric acid solution (or maybe vise versa, can't quite
    remember) which stains the stone black. This process does not affect
    any precious opal in the matrix at all as it is not porous like the
    matrix. Personally, I don't think it looks like precious black opal
    at all. The only name I've ever heard it given is just plain old
    "treated matrix". 

    Since my Pa spent a couple of winters for digging opals at Andamooka
    and Ma had fun treating a lot of matrix, I can spot a treated matrix
    a mile off. 

Renate, Adelaide, South Australia 

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