black opal
mineral
Quick Summary
Black opal is a dark-colored variety of opal that displays red or green internal reflections. Opal itself is a silica mineral, a submicrocrystalline form of cristobalite, and was once considered a noble gem. While opal is fundamentally colorless, impurities can give it various body colors, including black, which is often due to manganese oxides and organic carbon. Black opal is particularly rare and highly valued, distinguished by its dark gray, blue, or black body color. Precious opals12
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