Liddicoat, Richard T., Jr. Gemological Institute of America, Los Angeles, California.
Last reviewed:December 2019
- Additional Reading
The name onyx is applied correctly to banded chalcedonic quartz, in which the bands are straight and parallel, rather than curved, as in agate. Unfortunately, in the colored-stone trade, gray chalcedony dyed in various solid colors such as black, blue and green is called onyx, with the color used as a prefix. Because the color is permanent, the fact that it is the result of dyeing is seldom mentioned.
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