Is this White Topaz or Synthetic?

[cellentani]

I know it's impossible to tell for sure without having it tested, but I don't think it's worth sending off. This stone was preset in a ring purchased around 15 years ago (anyone remember Service Merchandise?) I swapped out the white stone for a blue topaz (SM offered jewelry repair), and I asked the jeweler if it was a cz. After scrutinizing it for a minute (no loupe or scope), he said it was probably a white topaz because of the RI. Recently, my local jeweler looked at it under the microscope, and he said it was a cz because the stone was scratched. I'm not saying he's wrong, but wouldn't a topaz be even more prone to scratching than a cz?

So, can any of you more seasoned gem lovers tell anything from my pics? It does have some damage (maybe a chip?) and the facet meets are a little rough and worn. And of course I had to be wearing a turquoise shirt when I photographed the stone.

I'm only going to post 4 pics, but I can post more if necessary. And none of the photos have been color adjusted or sharpened.

 

[cellentani]

Closer

 

[cellentani]

.

 

[cellentani]

?

 

[Richard M.]

Hi,
You''re right that no definite ID can be made without actual testing. But here are some clues:

1. Your images show lots of dispersion in the stone. That''s a very strong indication of CZ, which has about 1.5 times the dispersion of diamond. Topaz has very low dispersion as do most other relatively inexpensive colorless natural stones.

2. Service Merchandise was a mass merchandiser. They sold many synthetics.

Richard M. (Rick Martin)

 

[cellentani]

Date: 8/6/2009 12:27:20 PM
Author: Richard M.
Hi,
You''re right that no definite ID can be made without actual testing. But here are some clues:

1. Your images show lots of dispersion in the stone. That''s a very strong indication of CZ, which has about 1.5 times the dispersion of diamond. Topaz has very low dispersion as do most other relatively inexpensive colorless natural stones.

2. Service Merchandise was a mass merchandiser. They sold many synthetics.

Richard M. (Rick Martin)

Thanks for weighing in. So you think that''s dispersion, instead of my blue shirt reflecting in the stone? I''m gonna change my shirt and take new pics. And yes, SM did sell a lot of synthetic sapphires and rubies (and dark, murky garnets)!

 

[Michael_E]

Tilt it. Topaz has a pretty low refractive index and so tilting it will show a "tilt window" through the table almost immediately. CZ has a much higher index and so it needs to be tilted to nearly 30° to show a small, dark triangular window.

 

[cellentani]

Date: 8/6/2009 12:50:09 PM
Author: Michael_E
Tilt it. Topaz has a pretty low refractive index and so tilting it will show a ''tilt window'' through the table almost immediately. CZ has a much higher index and so it needs to be tilted to nearly 30° to show a small, dark triangular window.

Well, that pretty much seals it - I''m tilting the stone quite a bit in the photo, and even though it''s a little blurry, no window. Wow, I''ve never actually hoped to see a window in a stone before. Thanks Michael.

 

[chrono]

Yup, too much coloured light return for a white topaz. And the window tilt test does it again.

 

[CharmyPoo]

I have several white topaz (including the one that was on Barry''s site). They don''t look like the stone in your photos.