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Acid polishing Coral?

 while he would confirm it was being used on red coral, he would
not tell me what the acid was. He did indicate that they just
'painted' it on and then neutralized it (I guess with soda). 

Coral chemically is very similar to the Mexican ‘onyx’, that is
mainly calcite. I would think that what ever is used on onyx can be
used, though it may need to be more dilute, on coral.

My observations. From Slowly warming, I think spring actually may
have found us, Calgary, Alberta, Canada.

Karen Seidel-Bahr the ‘ROCKLADY’ @Rocklady K.I.S.
Creations May your gems always “Sparkle”


All, I can’t think of a single good reason to use acid to polish
Coral or any other calcite gem or ornamental material. It is done in
foreign factories for the sake of productivity, but I am afraid that
it is a very dangerous practice which is deleterious to the health
of the workers. Mexican calcite onyx is usually polished using
oxalic acid. Oxalic acid is poisonous and cannot be justified as a
shortcut in polishing inasmuch as polishing nearly always introduces
microscopic particles and droplets into the atmosphere and it is
nearly impossible to screen them out. Coral and other calcium
carbonates can easily be polished on a conventional wheel using Zam
or similar compounds. Risking ones’ health for a few pennies saved is
ludicrous ! Ron at Mills Gem, Los Osos, CA.


No arugment there Ron…Lest there be any misunderstanding…the
question was asked about using acid to polish and some of us merely
mentioned situations we were aware of when it was used as such. My
comment re use of acid to polish coral was based on from
the 1970’s which I believe was BZ (before ZAM). White diamond was
around then and works pretty well also, but in Taiwan ATT they didn’t
have some of the choices then as here in the States. Oh also, that
was an industrial situation and the working conditions in those
foreign factories were abysmal to say the least. They have come a
long way since then!

My article on black coral that appeared in Aug 2000 edition of LJ
calls for ZAM as the polish of choice for coral.

Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry! @coralnut1