Gems

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Some clear/clearer precious stones, like diamonds and rubies, refract light in a way that makes them appear more opaque than others. However, even these stones are not completely solid; they contain tiny air pockets or inclusions that can cause their transparency to vary. Some of the most transparent gems include opals, which have microscopic scales that diffract light, creating a play of colors, and quartz crystals, which can be so clear that they appear almost invisible.