It is with great sadness I'd like to announce Dr. Hanneman passed away on December 12, 2020. His legacy will live on forever!
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PostPosted: Thu Oct 29, 2009 9:27 am 
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You can just explain during the chat! :wink:


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PostPosted: Thu Oct 29, 2009 10:10 am 
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The GIA lists a Chelsea in a paragraph in a section called "Occasional Tests", Chapter 35, Gem Identification Course.
Quote:
The Chelsea Color Filter is used to detect dyes in certain gems, to indicate the coloring agent in some gems and to separate some gem materials from common imitations. It is a simple, inexpensive device, and thus, a popular piece of gem testing equipment in jewelry stores. Some dealers who examine large quantities of gems fid the Chelsea Color Filter handy for detecting synthetic blue spinels that sometimes get slipped into parcels of aquamarine.
RESULTS: The following are some color Filter reactions that may help you identify certain gems.
-Synthetic blue spinel: pink to red
-Synthetic Blue Quartz: pink
-Blue Cobalt Glass: pink to red
-Dyed Green Chalcedony: red to orange-red to pinkish orange
-Dyed Blue Chalcedony: red to pink to pinkish orange
-Dyed Blue Howlite: pink or red
NOTE In addition to the materials listed above, some others may change color under the Chelsea color filter-but this may or may not aid in identification. Emerald turns red, for example-but, so does synthetic emerald. Demantoid garnets and some green zircons look pinkish or reddish through the filter, and thus could be confused.Thus, although the Chelsea color filter may be a useful supplemental test, the results give only an indication, not proof of a stone's identity


When I attended DGemG, it was never mentioned.


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PostPosted: Thu Oct 29, 2009 1:39 pm 
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Interesting. I went to the Gem-A conference a few weeks before, Antoinette Matlins (she was one of the speaker, and her topic was "After 75 years, the Chelsea Colour Filter still proves its worth") has convinced a lot of the attendees that CCF is useful.

I am definitely here on Sunday for Brian's talk. :)

P


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PostPosted: Tue Nov 03, 2009 12:45 am 
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I will be out of town this coming weekend. If it is of continuing interest, we'll try to tackle the "color center electron trap" the following weekend. The whiteboard was pretty effective this past chat, so we'll use it again.


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