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 Post subject: distinguishing natural aluvial corundum rough from heated??
PostPosted: Sun Dec 24, 2006 7:38 am 
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Joined: Wed Oct 18, 2006 6:20 am
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Location: thailand
hi,i thought i'd ask here as you guys are examining rough more than most.
regarding exterior observasions of rough corundum;
does heated corundum rough generally always have a smooth surface & is the shape of heated material random,or very similar to how it came out of the ground?
& does aluvial,waterworn etc,corundum rough still generally have a pitted surface,or can it resemble the heated stuff.

many thanks

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PostPosted: Sun Dec 24, 2006 2:35 pm 
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Location: Southern California, U.S.A.
Hi,
Others like Vincent with more direct experience in that market will no doubt respond. But let me add my own experience.

Corundum is usually heated after cutting but there's no reason rough can't be heated. I've had it done just to test the potential for improvement by heating. If the rough is alluvial it would come out of the oven slightly shiny, coated with glass-like flux.

Anyone wishing to deceive could easily remove the flux and restore the corundum's original natural alluvial appearance merely by tumbling it for a suitable time with silicon carbide abrasives. I have no idea whether this is actually done but it's certainly possible. I wouldn't use appearance as stated in your post to judge heating/no heating.

Rick Martin


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PostPosted: Sun Dec 24, 2006 6:19 pm 
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I'd imagine that your best bet would be to polish/cut a small window and look inside for diagnostic inclusion phenomena which would either suggest or counter-indicate heating.


Last edited by gem-n00b on Mon Dec 25, 2006 1:20 am, edited 1 time in total.

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PostPosted: Sun Dec 24, 2006 6:23 pm 
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According to Richard Hughs many synthetics are shaped into natural crystal shapes then tumbled to make them look like water tumbled naturals. I guess the same can done to disguise heated stones... If there's a dollar to be made and it can be done then I think it safe to assume that it has been done

be well

Frank


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