Opal: " For in them you shall see the living fire of the ruby, the glorious purple of the amethyst, the sea-green of the emerald, all glittering together in an incredible mixture of light." ~ Roman Pliny the Elder on Opal, Century AD--iridescence
Black Opal is Australia’s national gemstone. Found in the Lightning Ridge area in northwestern New South Wales, black opals are natural, solid stones that absorb scattered white light, giving it brilliant spectral colors.
Opalized snail shell from Coober Pedy, South Australia; one of the leading opal mines in the world. Also, read more on Coober Pedy. One of the hottest places in the world, yet residents live in honeycomb caves that stay nice and cool all day.