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PostPosted: Mon Jan 07, 2008 6:55 pm 
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Well, here's hoping it's CZ... we'll know in a few weeks. :)


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PostPosted: Tue Jan 08, 2008 2:39 am 
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Rick,

There is indeed a remarkable similarity. I hope you are right on this.

J-

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PostPosted: Tue Jan 08, 2008 4:02 am 
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Jason,

What is interesting is that in the picture, the zircon shows facet doubling, but in the video it doesn't look as if there is any. The back facets are sharply visible at times and there doesn't look to be any of the "slightly out of focus" effect.


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PostPosted: Tue Jan 08, 2008 4:07 am 
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I noticed that too. But, I'm thinking it may have to do with shutter speed. I have seen high quality photos of Zircon that show very little facet doubling...almost non apparent...and other pics of the same stone...taken with different settings...in which the doubling was very pronounced. Since video is necessarily shot at a much faster rate than a still photograph, I'm wondering if it might not be able to "catch" the doubling as well.

THoughts?

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PostPosted: Tue Jan 08, 2008 2:14 pm 
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Quote:
THoughts?


I'm not sure that this has much to do with the shutter speed or photography as it does the directional viewing.

I see strong doubling or birefringence as the stone is turning. Notice the pear shaped stone is laying on it's side on one shoulder. As the stone spins, notice the shoulder of the pear that is at the top of the image as it comes into view from the pavilion side. You should see the strong facet doubling there as well as through the table in certain directions.

It just happens fast with the moving object.

You can do this simple demonstration yourself by holding up two fingers together in front of you. Consider the two fingers to be the facet doubling. Now rotate your wrist until you only see one finger. You are now either looking parallel down the optic axis (a direction of single refraction in a DR gem) or you are looking perpendicular to the optic axis which would be the direction of maximum birefringence, but, you would not see the facet doubling because the images are directly in line with each other. Like your fingers are when you rotate your wrist.

Well OK, maybe not the greatest example in the world, but, a reminder that you should always look in more than two directions when trying to observe birefringence/ facet doubling.

P.S. If you are running IE7 with the zoom level feature in the bottom right corner of the tool bar, use it to get a larger image of the zircon video. The doubling will be easy to see using the zoom feature.


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PostPosted: Tue Jan 08, 2008 3:36 pm 
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JB wrote:
You can do this simple demonstration yourself by holding up two fingers together in front of you. Consider the two fingers to be the facet doubling. Now rotate your wrist until you only see one finger. You are now either looking parallel down the optic axis (a direction of single refraction in a DR gem) or you are looking perpendicular to the optic axis which would be the direction of maximum birefringence, but, you would not see the facet doubling because the images are directly in line with each other. Like your fingers are when you rotate your wrist.

Well OK, maybe not the greatest example in the world, but, a reminder that you should always look in more than two directions when trying to observe birefringence/ facet doubling.


JB, that was one of the most relevant analogies I've ever heard regarding the optic axis. It made some puzzle pieces fall into place, so for me it was the greatest example in the world! Thanks!! :smt042

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 Post subject: Chinese Ebay "Zircon"
PostPosted: Tue Jan 08, 2008 5:43 pm 
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I purchased a bunch of "zircon" from a Ebay seller from China, who subsequently had to change his advertizing to reflect the true nature of what he was selling, i.e. CZ. And I guess his Paypal account was garnished. :lol:

AMEX refunded me the $100 or so I sent Paypal, Ebay may have lost out, and I hold the goods for the US Postal Inspector in case they ever want to investigate fraud through the mail. I don't return fraudulant sales. I hold the evidence. :twisted:

I wasn't exactly ignorant of the fact that I wasn't going to get what they said they were selling, but did the purchase anyway to prove a point to Ebay :wink:

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PostPosted: Tue Jan 08, 2008 6:13 pm 
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The first clue on Ebay is when they offer 100ct sizes not seen in natural zircon at pennies per carat.

I have not yet seen the real research synthetic zircon, but I don't believe any is in commercial production. I'd be interested in some when it becomes available, but you are probably not going to see it on Ebay anytime soon.

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PostPosted: Tue Jan 08, 2008 11:15 pm 
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Crystal Star wrote:
JB, that was one of the most relevant analogies I've ever heard regarding the optic axis. It made some puzzle pieces fall into place, so for me it was the greatest example in the world! Thanks!! :smt042


Image
Image

These images show a little more "mineralogical" example :D Same calcite crystal, two different orientations.


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PostPosted: Mon Jan 14, 2008 1:41 pm 
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There is some nice zircon coming out of Tanzania. Usually it needs to be heated to get the best color. Ive explained the simple method in other posts here.

Below is one from Tanzania that I recently cut.


Image

But I have seen some that will heat to a pinkish color also. I just bought one very large piece, I think it's about 44 cts, that is well shaped and should cut about a 12 ct or more finished stone. Right now it's almost black, but after heating it should be a bright red color. The dealer in Kenya I got it from showed me a cut piece he heated, and it was spectacular. Not as light as the photo from Jason above, but much much better than what Barbra ended up with.

I've always thought that many of the gem photos on Ebay are colored and enhanced.

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PostPosted: Fri Mar 14, 2008 8:56 pm 
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The scary thing is that I wonder how long these have been available and if it's possible to grow it with more "convincing" hues (i.e., not as bright and super saturated)...


I've ben browsing ebay since about 2004 or so and at that time the ebay US was PACKED with these synthetic zircon xls (most oftenly adversited as being from Sri Lanka if memory serves me). They are much more scarce by now.


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PostPosted: Mon May 05, 2008 9:58 am 
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Pink zircon from tanzania is not a new find. I have been buying in smaller fine parcels for a long time. Supply has been sporadic. Some of these pink and purple zircons heat to yellow, however I have no idea why someone would want to do that. They range from pinkish, to mauve, to purple, to orange pink, and on the whoe run fairy clean. They cut beautiful stones. I buy rough direct from a tanzanian dealer, and he almost always has it in stock.

The other place pink and purple is found regularly is the Harts ranges in central queensland in Austrlia. colours again vary, but rought in 100+cts is common. Colours paler on the whole than tanzanian material, and pinks usually have a copper undertone.

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PostPosted: Sat May 17, 2008 3:23 am 
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There are still lots and lots of suspicious zirkons out there on ebay. But now theyre mostly 'natural' cambodian zirkons. I just bought three huge perfect specimens for 0.99 a piece. :P

I need the reference and didn't have any cz in my collection. :)


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PostPosted: Sat May 17, 2008 10:28 am 
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gem-n00b wrote:
Well, here's hoping it's CZ... we'll know in a few weeks. :)


Did you ever get this stone, Karim?


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PostPosted: Sun May 18, 2008 1:24 pm 
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After several back and forths with the seller, he stopped contacting me completely. I didn't feel it was worth pursuing the matter, he obviously didn't want to complete the sale for some reason.


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