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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.bio
Subject: Re: ivory vs. bone
Summary: Determination using density and UV fluorescence
Message-ID: <4140@kitty.UUCP>
Date: 27 Oct 90 04:10:12 GMT
References: <6102@videovax.tv.tek.com>
Organization: Recognition Research Corp., Clarence, NY
Lines: 44

In article <6102@videovax.tv.tek.com>, chrish@videovax.tv.tek.com (Chris Hawes) writes:
>        I'm seeking info on how to distinguish the difference between
> carved and polished bone vs. carved and polished ivory.  I have an antique
> that I have been told is worth 3X more if its ivory.  The antique is
> a vintage Mah Jong game made in the 1920's.   I took it to one biology 
> teacher, but she said the polishing made it difficult for a non-expert
> to tell whether or not it was bone.

	Old ivory has a higher percentage of collagen (like 30% or so) than
old bone (like 10% or so).  The density of ivory has little variation from
1.9 g/cm^3, while the density of bone varies between 1.7 and 2.0.  A density
much higher or lower than 1.9 can be used to *exclude* the presence of
ivory.  Density can be non-destructively measured using water displacement.

	An experienced person can usually tell the difference between ivory
and bone by visually examining its fluorescence under UV illumination.  As
I understand it, ivory has a more pronounced fluorescence, with "newer"
ivory being purple and "older" ivory being mottled yellow.  The above
fluorescence is different from that of bone.

	Chemical analysis can also be used, but I suspect it is not necessary
for your application.

> I would especially be interested
> in any info regarding the economics in the 1920's which would have in-
> fluenced the use of bone vs. ivory.  Obviously, the cost of ivory today
> is very high, but what is the cost of bone?  And what type of bone would
> have been used at that time to make handcrafted items?

	Sorry, but these questions are definitely out of my field!

> Should I trust an antique dealer with this question?

	Contact a museum or university to locate someone with a specialty in
archeology, anthropology, paleontology or antiquities conservation for an
impartial determination.
	
> How difficult is it to tell the difference?

	Probably not difficult for an experienced person.

Larry Lippman @ Recognition Research Corp.  "Have you hugged your cat today?"
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