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 Tanzanite extinction in cut??
P:  11/4/2006 10:51:11 PM  
ger100
ger100

Cut Rock
Total Posts: 169
Last Post: 11/20/2009
Member Since: 9/25/2006
 
 		I bought a 1.75 ctw (7.5 x 7.5) trillion Tanzanite, with no visible inclusions. It is a fairly dark purple-blue from the front. It flashes either blue or purple color from the top when you move the stone, depending on what angle the light hits it. Otherwise, just holding it, it looks kinda dull...don't know how to describe it.

HOWEVER, when you turn it over, it looks very light upside down, making it easy to see through the 3 sides. 2 of the sides are purple and one is blue!? I count 12 cuts on each of the 3 sides, some large, some small.

Could this darkness from the front be what Newman calls EXTINCTION?
And how badly does it affect the value?

Also, could some smaller cuts be added to the back to make it more brilliant??

I'd appreciate a fairly quick opinion, since I only have a few days to return it.

Thanks so  much!
Ger newbie
Posted:  11/4/2006 10:51:11 PM

 There are 3 replies to this message.  There are 3 replies on this page.
P: 11/5/2006 6:19:10 AM
Pyramid
Pyramid

Ideal Rock
Total Posts: 2,914
Last Post: 11/11/2009
Member Since: 11/10/2002
 
 		Just a consumer here but tanzanite does have a term where it looks a different colour from different angles.  The name of this is pleochroic.  One of the experts willl chime in about it.  I am not sure about extinction but I think this term is more to do with dark, unreflective areas where no light is returned to the eye and windowing where you can see straight through the stone..

Posted:  11/5/2006 6:19:10 AM
P: 11/5/2006 6:21:59 AM
Pyramid
Pyramid

Ideal Rock
Total Posts: 2,914
Last Post: 11/11/2009
Member Since: 11/10/2002
 
 		http://www.pricescope.com/idealbb/view.asp?topicID=13257&forumID=11&catID=&search=1&searchstring=

It is mentioned in this article.

Posted:  11/5/2006 6:21:59 AM
P: 11/5/2006 8:59:48 AM
C Smith
C Smith

Cut Rock
Total Posts: 176
Last Post: 4/1/2007
Member Since: 6/14/2006
 
Date: 11/4/2006 10:51:11 PM
Author:ger100
I bought a 1.75 ctw (7.5 x 7.5) trillion Tanzanite, with no visible inclusions. It is a fairly dark purple-blue from the front. It flashes either blue or purple color from the top when you move the stone, depending on what angle the light hits it. Otherwise, just holding it, it looks kinda dull...don't know how to describe it.

HOWEVER, when you turn it over, it looks very light upside down, making it easy to see through the 3 sides. 2 of the sides are purple and one is blue!? I count 12 cuts on each of the 3 sides, some large, some small.

Could this darkness from the front be what Newman calls EXTINCTION?
And how badly does it affect the value?

Also, could some smaller cuts be added to the back to make it more brilliant??

I'd appreciate a fairly quick opinion, since I only have a few days to return it.

Thanks so much!
Ger newbie




Extinction is a dark/black area in a gemstone viewed face-up where light is not being returned to the eye.



Ioilite is a rather extreme example of pleochroism, which is the showing of multiple colors. When viewed from different directions, iolite may appear colorless or blueish with no instruments required;
Posted:  11/5/2006 8:59:48 AM

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