Opal mining is still very much going on in and around Coober Pedy. Some people get rich, others just earn a meagre living. Although opals are quite beautiful, the author does not really see the point -  they simply consist of small (150-300 nanometer) spheres of  silicon dioxide, with about 20% water, creating their changing colour by diffracting light because its wavelength is about the same as the sphere center distance. No industrial value whatsoever. Actually, in his youth, the author has researched on "liquid opals", polystyrene colloidal crystals in very pure water... only disadvantage was that they would disappear when shaken even a little bit.