Hi Randy - good suggestion! If you don't have a portable gun,
A "poor man's probe" might also work by checking some of the physical
properties,
(1) An appropriately selected hardened steel file would be in the range
to scratch soda glass but not a moldavite;
(2) The refractive index of a Moldavite is slightly lesser than Soda
glass and might be measureable by a cheap Chinese refractometer
(3) Moldavites are about 5% lighter than soda glass so if you can
measure the volume by displacement, you could rule them out by density.
I've often wondered if there is an appropriate temperature to which a
moldavite can be safely heated, and then quenched in water or ice water
and survive fine. By pushing this test to the limit it could be
something that could be done in the kitchen by anyone on the fly. The
idea being that soda glass's expansion coefficient is greater and will
not survive the quenching and the moldavite will (in all cases ...
assuming an 'in all cases' is possible given the variety of natural
variations). I haven't compared the expanision vs. temperature of
these materials but it's probably easily googleable. I wonder what
Norm thinks?
Kindest wishes
Doug
-----Original Message-----
From: Randy Korotev <koro...@wustl.edu>
To: meteorite-list@meteoritecentral.com
Sent: Mon, Aug 1, 2011 4:41 pm
Subject: Re: [meteorite-list] New type of fake moldavite coming soon?
Unless these guys have gone to a lot of work making a special glass, I
would think the fakes could be easily be distinguished from the real
things by composition. Moldavites have less than <1% sodium as Na2O
whereas green bottle glass has 13-14%. Similarly, green bottle glass
(soda-lime glass) has 9-11% calcium as CaO whereas moldavites have 2-3%
CaO. Moldavites have 2-3% iron as Fe2O3 and green bottle glass (7
samples I've analyzed) has 0.1-0.7%. One of those hand held XRF guns
should be able to see the differences for Ca and Fe (they won't do Na
except in vacuum).
Randy Korotev
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