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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


#8

Posting pics of chrome tourmaline in daylight, in incandescent light w/chelsea filter & without filter incandescent light-steve…


#9

did you sell these already?
I am interested. I have bought a few already, but always love them. Yes they are changing color due to the usambara/path length absorption effect. The price will depend on how dark they are. Unfortunately, the effect is seen clearly on overly dark(high absorption) material, which of course make the stone less attractive and the color change harder to see.