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Color change Tourmaline Usambara


#1

Hello, I recently bought a lot of Tanzanian Tourmaline Chrome in an old stock over 10 years old. I noticed by chance that some Tourmaline changes color, one green / violet, another green / brown, and another green / greenblue. It’s not dichroism these a real color change, I think it was mined in Usambara.
I know tourmaline I often buy from any source, but I had never seen this kind of tourmaline, I have already certified one by the laboratory AIG Antwerp, but I have a lot of trouble to put a price on seeing the rarity, I already show the stones to a lot of confrere who had never seen either. they are small stones of - + 1.50ct a batch of 10ct but only 20% which changes.


#2


#3

Can’t see the pics clearly so blurred


#4

They look more like bicolor. Pleochroism will make tourmaline color shift/change.
But without actually seeing them I wouldn’t venture a guess at price.


#5

Very nice


#6

Hello, this is not the plechroisme like most tourmaline very plechroic. This is the effect usambara, a color change due to the high chromium content that appears with a change of wavelength 300Lm 2700K only. in video its more visible.


#7

Hello, we can see red flash appear in the dispersion due to the chromium content