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PostPosted: Thu Oct 04, 2007 4:44 pm 
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Brewster angle meter
Reflectivity meter (suitable scale showing approx RI)
Andersons immersion contrast effect (with the mirror underneath)
Immersion contact photography
Becke line method (Later developed by R K Mitchell using immersion techniques)
Bright line technique (Ok this one still needs a refractometer)


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PostPosted: Thu Oct 04, 2007 5:20 pm 
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Fabry-Perot laser interferometry
Microinterferometric Backscatter Detection
+ many more versions of using a laser+photodetector to determine refractive and reflective indexes.

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PostPosted: Fri Oct 05, 2007 11:04 am 
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Hi,

That is a nice list Frank.
Jung Kee, somehow I don't think anyone here will ever try to find out how those work.

Here is my list of alternatives to the refractometer:
* Immersion liquids used to compare the RI's (see if it disappears)
* Immersion liquids, Plato method (the Mitchell method Frank aimed at).
* Immersion liquids, Anderson method
* Becke line method (nice for inclusions)
* Shadow method (Wilde/Eppler)
* Nelson fingerprinting
* Hanneman pinhole refractometer
* Hanneman/Hodgkinson refractometer
* Hodgkinson's visual optics
* Real depth/apparent depth (microscope)
* Brewster Angle meter
* Table spectrometer
* Reflectance meters

Did I miss any?


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PostPosted: Fri Oct 05, 2007 11:21 am 
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Do you have a link to this "Nelson fingerprinting"? I don't know that I'm familiar with it... I just used some of my knowledge of physics to sort of "reason out" a method. Google didn't reveal much, so I'm hoping you have a site that you know about with "secret or esoteric" gemology knowledge. ;)


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PostPosted: Fri Oct 05, 2007 11:41 am 
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Hi,

http://www.pricescope.com/idealbb/view. ... icID=10635
http://www.scotgem.demon.co.uk/moisstest.htm


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PostPosted: Fri Oct 05, 2007 4:13 pm 
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Hi Doos,

The immersion contact photography technique doesn't seem to appear on your list.

If any of you have the ninth edition of BW Andersons gem testing published in 1980 then you can find some nice examples of what these photo's look like on pages 42 and 43.

Or maybe it's covered by one of the others on the list?...If you don't have the book doos (or anyone else) I'll scan the pages and send you them if you like.

Good quiz...Maybe we could discuss it this Saturday in chat? I know we're supposed to start on colour but Crystal say's she might not make it so we could put the colour chat of for a week till she's back? ...Guess I should have posted this on the chat forum...sowwy

Be well

Frank


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PostPosted: Fri Oct 05, 2007 4:19 pm 
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Hi Frank,

I think you mean the one that shows the outline of the girdle as a contrast (thick versus thin)?
That is what I name the Anderson method, you can either catch it on film or just use a small mirror.

See Anderson method


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PostPosted: Fri Oct 05, 2007 5:05 pm 
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Yes that's the one ...thick versus thin and dark versus light...In BW Andersons book they are described seperately though, reading back through it I see the sketch of the mirrors is labelled "viewing immersion contrast effects" and the section with the photo's is called "immersion contact photography"...so same effect described differently.


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