Boulder OpalsBoulder opals are similar to the black opals in that it has the same dark in tone. They get their name from the the fact that they form in the crevices found in boulders and can can vary drastically in size, for example from the size of a coin to the size of a car. The beauty of a boulder opal is that its natural finish can be extremely shiny and rich in colour.
Crystal OpalsCrystal opals are unusual for the reason that they have a transparent or semi-transparent look to them a lot like glass. What also makes the crystal opal interesting is that it can appear as either in a light or dark tone so you get an effect of a black or white opal that will be semi-transparent.
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