Opal is composed of small beads of silica – alpha-cristobalite – low temperature, but tightly closed in a waterproof casing. Between these “beads” have cavities that contain a small amount of water. Reflection of light on the surface of the opal crystallization gives reflections that differ from each stone depending on the “form” created by all the elements described above. There are many types of opal. Opal can be dull and have no value, in which case such opals called “common opal” because only the large stones of bright colors are “semi-precious opals”.
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