ONYX

Onyx is again another form of the microcrystalline quartz, Chalcedony, (as are Sard, & Sardonyx).

Onyx has straight bands which may be brown & white or black & white. It is formed from alternating bands of opal & chalcedony.

Since Ancient Egyptian times onyx has been stained to improve or change its colour. Onyx has been prepared by soaking agate in sugar solution then heating it with sulphuric acid to carbonize the sugar.

Onyx lends itself to the carving of cameos as the different layers can be carved away to reveal the colours.

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