Spring 2015 Gems & Gemology

[Marlow]

Top article about Cobalt spinel from Luc Yen and a very interessting article (pictures!) about Tucson 2015 !!!!

http://www.gia.edu/cs/Satellite?blobcol=gfile&blobheader=application%2Fpdf&blobheadername1=Content-Disposition&blobheadername2=MDT-Type&blobheadername3=Content-Type&blobheadervalue1=attachment%3B+filename%3DSP15.pdf&blobheadervalue2=abinary%3B+charset%3DUTF-8&blobheadervalue3=application%2Fpdf&blobkey=id&blobtable=GIA_DocumentFile&blobwhere=1428769026302&ssbinary=true

Cover your keyboard !!!!! Sabber sabber.....

 

[LoversKites]

I downloaded it now just to see the pics -- I'll read some later

 

[minousbijoux]

Marlow:

Is it common for Be to be part of the chemical composition, or is it just a fluke of these samples (p.10 has the table, p. 11 has the quote)?
"Samples SKYBLU1 and GREBLU2 were enriched in Be and Zn compared to SATBLUchem. GREBLU2 is also enriched in Li and Ga compared to the two others."

ETA: and I like the description of the telltale inclusions - i.e., not many!

 

[Marlow]

Yes,

you will always find other elements like Be, Li or Ge and Ga.**

One of the most important gemologist - Dr. Gübelin - said that there is no Cobalt in Spinel!!
Today we know that Cobalt is the main coloring agent in these kind of spinel - not the quantity - the quality is important!!
Cobalt is a very very strong coloring agent - so you need not much.


** A gem like Taaffeite (Sri Lanka, Tanzania and Burma) for example - I am sure if they collect enough material from trusted sources
they would be able to say which taaffeite is found in Sri Lanka or Burma or Tanzania.

But I bought a few small very faint purplepink stones - my vendor ( from Sri Lanka) says there are from Sri Lanka ( cut in Sri Lanka).
I bought a similar colored one from Burma two weeks ago (small cushion 0,41 ct) - and this stone and 4/5 of the Sri Lanka stones show
an orangepink LW fluor!! Normally taaffeite is inert to LW UV - even the chrome rich red taaffeite from Sri Lanka is inert!!! NO article describes orangepink LW UV till today! Green and white and one!! red taaffeite with red fluor.

I believe the factory bought rough from Burma ( the cut Ruby too) - the burmese taaffeite is very low in iron ( fluor killer) with a little chrome. We will see - I will collect some more - maybe somebody is interested to do some research about them.