A Mystery solved.... those little blue melee.....

[Bron357]

Amongst my loose gem haul was a pile of blue melee. Various shades of violet blue. I cheated (these are too tiny for doing a SG reading or even a dichoscope) with a Presidum.
To be honest, such a pretty blue I assumed glass, no, then sapphire, no again. Testing on the Presidum I’m registering in the upper Tourmaline range. Ok, tourmaline.
Then later I noticed a bizarre thing, in the container, when on their side they seem to have a reddish tint. Weird, so I washed them thinking maybe the rusty tins they were stored in had put some sort of rust on them. No change.
Then I noticed another thing, even though face up they are the nice bright blue, they also go a deeper purplish colour at some angles.
Then the light bulb moment!
Upper range tourmaline on a Presidum is also Tanzanite.
Tanzanite display pleochroism, three colours depending on crystal orientation - bright blue, darker purple blue and burgundy.
So these are Tanzanite melee.
Mystery solved.

 

[YadaYadaYada]

Beautiful color, I love the reds and purples showing on the stones in the container.

 

[rockysalamander]

What a lovely find!

 

[voce]

Ooh...excellent! Mystery finally solved.

 

[leslie1956]

Beautiful shade of tanzanite, too, congratulations!

 

[chroman]

Your lot of adventure just keeps on giving!
Love that color also!

 

[Bron357]

Thanks everyone. I was a bit embarrassed that I didn’t twig earlier. Mind you I’ve never owned any Tanzanite. They truly are a fabulous neon colour. I also have similiar size hot pink tourmaline so I’m tempted to do a “tutti fruitti” band ring alternating bright blue and hot pink !

 

[arglthesheep]

Hi Bron,
i hope i am not too negative, but normally small tanzanites do not have this intense color. So this color i never saw in small melee size tanzanites. I would suspect something else or probably coated/infused material...
Sorry for bothering

 

[Bron357]

Hi Bron,
i hope i am not too negative, but normally small tanzanites do not have this intense color. So this color i never saw in small melee size tanzanites. I would suspect something else or probably coated/infused material...
Sorry for bothering

Well I didn’t think of that. A lot of trouble for such wee little things. They are old stock, at least 20 years old, so I don’t know what treatments might have been around back then? They aren’t coated or anything, I broke one apart to check and so ?
Is there any other test I can do ? I presume they are heated but I checked and apparently they can't make synthetic Tanzanite - so I figured given their 3 colour spectrum, Tanzanite.

 

[arglthesheep]

You have a refractometer? this would be of great help to narrow down the possibilities.
Do you have a chelsea filter?
The pleochroism is interesting as it rules out a few things.
Normally if a tanzanite is heated he wont show 3 colors anymore in my knowledge. But this intense color makes me suspicious.
https://www.gia.edu/gems-gemology/summer-2008-coated-tanzanite-mcclure
I have a different article in mind, i cant find at the moment...

 

[arglthesheep]

http://www.pgmc.co.za/resources/pdf/newsletter/2009/pgmc_sep09.pdf
page 6 lower half....

 

[Bron357]

You have a refractometer? this would be of great help to narrow down the possibilities.
Do you have a chelsea filter?
The pleochroism is interesting as it rules out a few things.
Normally if a tanzanite is heated he wont show 3 colors anymore in my knowledge. But this intense color makes me suspicious.
https://www.gia.edu/gems-gemology/summer-2008-coated-tanzanite-mcclure
I have a different article in mind, i cant find at the moment...

Yes, I did do some research. I couldn’t find much on synthethic tanzanite, there are some “look alikes” but they seem to be synthethic spinel or corundum - just the blue purple colour.
Apparently they can’t be colour diffused (like rubies or sapphires) because the replacement atom is 30 times too big to take up a spot in the lattice! The only treatments noted are dyeing / a surface coating.
They already had a good wash because I originally thought the reddish tint on some of them (not actually all of them btw) was rust or something. And I did actually break one up to check under the microscope if it was a coating. No. I also checked UV, no response, so that’s often a give away for the synthetic tanzanite replicas.
Unfortunately I don’t have a refractometer or Chelsea filter as yet - on order - (only a microscope, UV light, spectrometer and dichroscope ) and they are way too small for doing a SG reading. Though I might buy an electronic one if I can be sure they give an accurate and reliable result.
The Presidium Gem tester (I know not a proper gemmological tool!) definitely gives them a thermal reading in the tanzanite range. This is well above “glass” ie CZ and well below Spinel or Corrundum so I sort of ran out of other gem options.
They are definitely old inventory, the jeweller guy died in the late 1990s and these (and a pile of other gems) were found hidden in an cardboard box the bottom of an old wardrobe.
So the mystery maybe remains and deepens......

 

[Bron357]

So the investigation continues..... this one is slightly larger (oval) and I sort of got a photo down the microscope using my iPhone (so high tech - not!) here, face down, you can see the burgundy “bit” and the inclusions which are apparently called “needles”. The other photo is it just sitting face up.

 

[chatoyancy]

Whatever they are, your mystery melee has lovely color.