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 Post subject: The Ultimate Challenge
PostPosted: Sun Feb 11, 2007 3:36 pm 
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The above picture contains 12 colorless, round faceted gems, with 12 unique identities. :shock:
It is my task ( 8) because I have chosen to accept it) to positively identify all these gems.

Let's see what we can find out.

The first thing I'm going to do is weigh all the gems and measure them. If I get confused, or the gems get mixed up, I can put them back in order again. The most useful measurements are the weight and the depth (although I have also taken diameter measurements).

A. 1.763 ct.; 3.93mm depth
B. 0.091 ct.; 1.71mm depth
C. 0.319 ct.; 2.63mm depth
D. 1.476 ct.; 5.05mm depth
E. 0.820 ct.; 3.61mm depth
F. 0.254 ct.; 2.54mm depth
G. 0.233 ct.; 2.74mm depth
H. 0.623 ct.; 2.56mm depth
I. 0.316 ct.; 2.87mm depth
J. 0.329 ct.; 2.29mm depth
K. 0.313 ct.; 2.32mm depth
L. 0.647 ct.; 3.25mm depth

Secondly, I'll test them with the Thermal Diamond Tester:
B and E register to be diamond, all others not.


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PostPosted: Sun Feb 11, 2007 9:40 pm 
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Sounds like fun! Please let us know the results :D .

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PostPosted: Sun Feb 11, 2007 11:44 pm 
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We know that if a stone reacts as "diamond" to a thermal tester it can be diamond or moissanite.
I found a zircon inclusion with a radiation halo, extra facets and no doubling of the facets in gem E so that is the diamond.
Since all 12 gems are different, that means B, by elimination, must be moissanite. Looking at it thru the table, there was no apparent doubling of the back facets, BUT when viewing the back facets and culet thru the upper bezel facets, doubling was obvious.
So so far:

B: Moissanite
E: Diamond


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PostPosted: Sun Feb 11, 2007 11:53 pm 
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Barbra - do you have the Presidium Multi tester that will separate moissanite from diamond?

If you do - I was just wondering if it gave you a false reading?

I love this thread! It brings back good memories of my Gem ID course!


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PostPosted: Mon Feb 12, 2007 1:59 am 
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No, I just own a regular thermal tester. That's why a "diamond" result can mean one of 2 things. :wink:


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PostPosted: Mon Feb 12, 2007 2:23 pm 
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Good game Barbra...whats next? Will you see how many of them give you an RI reading or use the polariscope to sort cubic from the rest?


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PostPosted: Mon Feb 12, 2007 3:38 pm 
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Yeah.
I'm going to collect information and than move this over to the quiz section later in the day. The stone I am working on now is giving me grief.
:x I'm going to take a break.


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PostPosted: Mon Feb 12, 2007 4:40 pm 
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Try the pavilion flash method, SG, and then the dispersion method - as I believe you have the testing liquids.

I think I posted photos of these methods in other threads over a year ago.

I wish I was there testing those stones with you - I love the colorless separations!


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PostPosted: Mon Feb 12, 2007 5:04 pm 
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Could this be the thread you are thinking of?
http://gemologyonline.com/Forum/phpBB2/ ... 25&start=0


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PostPosted: Mon Feb 12, 2007 6:06 pm 
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Why yes, there it is now! :D


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PostPosted: Tue Apr 22, 2008 11:02 pm 
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Could you list all the stones they could be, all the colorless ones? Or is that just vast? Would clear/white sapphire be an option? I guess one has to be a CZ.
Are they alll untreated, unheated, non-synthetic?


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PostPosted: Tue Apr 22, 2008 11:50 pm 
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Shoot...this one fell through the cracks. I identified these stones and them sent them back to the owner, without finishing the thread.
As I recall the set had
diamond
moissanite
quartz
colorless sapphire
YAG
GGG
strontium titanate
cubic zirconia
colorless topaz
colorless synthetic spinel
zircon
synthetic rutile

But I can't remember which one was which one at this point.


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PostPosted: Thu Apr 24, 2008 11:28 am 
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You could have characterized them all by their RI using the Method of B.W. Anderson. See my book, pages 132-7.


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PostPosted: Thu Apr 24, 2008 11:38 am 
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I used a combination of thermal tester, polariscope/consicope reaction, RI, dicroscope, SG, UV, Spectroscope and Microscope.

People often point out that my system is too labor intensive, but I have a large table set up with instruments in order and the time it takes to walk around the table, I can get all the specs. :D


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PostPosted: Thu Apr 24, 2008 2:55 pm 
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Great challenge! where did you get the stones?

dev's been collecting all different types of clear stones to harrass me with when I do my gem id course...he's such a sweetie :twisted:

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