[meteorite-list] Moldavite Update

[Norm Lehrman]

All,

I have access to a PIMA (portable infrared mineral
analyzer).  These operate on spectral reflectance in
the SWIR spectrum (1300-2500 nanometers).  There are
excellent water absorption features in this range. 
I'm sure I've run tektites before, but never in direct
comparison with volcanic and man-made glasses.  I'll
do this next time  I'm back in the office and report
back.  I do still have one of the chinese bottle-glass
pseudotektites somewhere if I can find it--

Regards,
Norm
http://TektiteSource.com

--- mafer at imagineopals.com wrote:

> Greetings Doug and List
> 
> There may be a non-destructive test that isn't as
> costly as a microprobe
> for tektites.
> 
> XRF was used by the Geology & Archaeology
> departments at WWU to check a
> flake (known artifact) against normally prepard XRF
> samples for composition
> similarities (for tracing the source outcropping of
> the material that flake
> was made of). This proved to be a viable alternative
> to destructive testing
> of artifacts, as long as exact results were not
> required and a relatively
> flat surface could be presented to the XRF and the
> sample would fit into
> the recepticle. It was thought that XRD would also
> work as well, given the
> same restrictions.
> 
> Many universities would have these devices, as
> opposed to those that have
> microprobes. And it would be a matter of setting up
> a database with known
> trace elements/minerals and look for the same in the
> XRD or XRF results.
> 
> 
> Just a thought.
> 
> Mark Ferguson
> 
> 
>  
> 
> 
> On July 21, 8:55 pm MexicoDoug at aol.com wrote:
> > John G. wrote:
> > > Since moldavites are made basically of the same
> material as green
> > > pop bottles, checking the refractive index of a
> faceted stone
> > > wouldn't turn  up anything suspicious...looking
> for new technology
> > > to tell the  difference between the fakes and
> the real stones.
> >
> > Hola John, List,
> > Not as easy as looking at a Shirokovsky
> 'pallasite', either, where
> > just one fake is well known.  This seems a lot
> scarier than getting a
> > "synthetic" diamond in place of a "real" one since
> an appreciation of
> > history is what makes the glass authentic for the
> owner, like a
> > winning game ball, and for the sake of  science a
> confidence in it
> > being of tektite origin necessary for future
> ability to study
> > composition of a real sample is at stake.
> > In the case of tektites, unless you have the
> ability to make
> > non-destructive measurements with expensive
> microprobes, I guess the
> > technique of choice will need to hinge on the
> difference tektites
> > have over  man-made glasses: low water content.
> >
> > Water has major IR absorbance peaks at 3550, 3425,
> 3295, 1630 and
> > 1455 /cm. An appropriately set IR analyzer at one
> or more of these
> > frequencies ought to be able to able to make a
> positive
> > identification vs. other  glasses (and confirming
> your refractive
> > index wouldn't hurt at all).  While  I've never
> done these types of
> > IR measurements in glasses, it would seem that 
> all you just need to
> > watch out for would be humidity, and to know your
> sample  path length
> > reasonably.  Other tests would rely more on
> variable criteria
> > depending on recognizing characteristics of the
> fake, sometimes easy,
> > but  sometime not. Tektites should yield about
> 0.001% to 0.03% water,
> > with  moldavites a very typical 0.01% (100 ppm). 
> I don't know what %
> > water  recast glass from coke bottles, etc., but I
> am guessing it
> > would be much higher  unless great pressures and
> long times in the
> > casting furnace were  used.  Anyone know the
> solubility of water in
> > glass at melt  conditions?  I'm guessing - 10 -
> 100 times that
> > amount? Saludos, Doug (where the neighborhood
> streets are still a
> > grid of rivers, in  the aftermath of the fight
> between Emily  and our
> > mountains.   Emily lost decisively as her Eye
> passed 80 km south.)
> > It is  refreshing to see water under the USD
> 50,000,000 bridge we
> > just built over the  otherwise dry riverbed.  The
> collosal "bridge"
> > is a copy of the  one in Rotterdam for our inland
> city nicknamed
> > "City of Mountains" nestled in  the Sierra
> Madre:).
> > ______________________________________________
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> >
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> >
> 
> 
> 
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