Mexican fire opals are named for their uniform flaming orange or cherry red body color. They are always very brightly colored, and can be a little bit cloudy to almost perfectly transparent. Transparent specimens have a good luster. Like the traditional opal, fire opals can occasionally display signs of iridescence in very bright light. Fire opals have a very low density, lower than that of glass, with which it is sometimes confused. Fire opals, like other opals, are relatively hard, rating a 5.5 to 6.5 on the hardness scale....
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