onyx (chalcedony) before color treatment
yellow onyx pendant & green garnet necklace
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| composition | silicon dioxide |
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| name source | from the Greek word onux, meaning "fingernail" (alluding to its weak transparency) |
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| other accepted names | black agate |
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| historical aliases | "stone of sadness," "stone of egotists" |
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| color | black (natural); black, gold, blue and other colors when dyed |
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| significant sources | Brazil, India, Madagascar, Uruguay and throughout the world |
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| MOH scale | 7 |
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| care and treatment | To clean, rub lightly with a soft polishing cloth. An optional dab of olive oil will produce a beautiful shine. If necessary, a plain water rinse may also be used. Do not soak, especially in an ultra sonic jewelry cleaner (or dyes may be removed). |
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