January 24 Through February 4—TUCSON, ARIZONA: Annual show
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 Post subject: Color change pyralspite beads
PostPosted: Fri Mar 16, 2018 9:33 pm 
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I went to the San Mateo Gem Show today and found my favorite dealer for gem beads.
As usual, he (Kit owner of Gem House USA, Inc) had some truly unusual gem beads.
He showed me a strand of color change garnet beads.
I bought a strand, a little stretch, not inexpensive....but worth it.
Standard gemological instruments:
Refractometer: 1.78
Polariscope: ADR
Gemmoraman: Paralspite: Red Spessartite
Image
Rare earth magnet picks up individual beads.
Some pics:
1. liquid feathers, intersecting rutile needles at 90º (trust me) and apatite xls. Some inclusions, I can't identify.
2. Rutile needles
3. Backlit: bug juice
4. Incandescent light...generated by an option on my camera, proved unreliable. The beads still looked bug juice.
5. On my kitchen counter in a sunbeam. Raspberry. That is still accurate.....although I now believe some of my incandescent dining room light tainted my findings.


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 Post subject: Re: Unusual (reverse?) color change pyralspite beads
PostPosted: Sat Mar 17, 2018 6:08 am 
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The color change would be extreme if the last pic is incandescent light and the 3th and 4th daylight...

But reverse CC!!!????? :shock:

No magnetic reaction??? Unusual for spessartine.

I have two CC pyrope with low RI but they have a strong magnetic reaction??

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 Post subject: Re: Unusual (reverse?) color change pyralspite beads
PostPosted: Sat Mar 17, 2018 12:17 pm 
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I tested the magnetism when the beads were on their temporary string. I'll take some beads off and try individuals.


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 Post subject: Re: Unusual (reverse?) color change pyralspite beads
PostPosted: Sat Mar 17, 2018 4:04 pm 
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All my CC garnets except the two pyropes have a RI around 1,76...

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 Post subject: Re: Unusual (reverse?) color change pyralspite beads
PostPosted: Sun Mar 18, 2018 12:06 am 
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What a difference a day makes.
I unstrung all my beads to restring them with some silver beads and a clasp on transparent steel reinforced cord. (holes are too small to properly string on silk)

I was in my incandescently lit dining room and all the loose beads looked raspberry.
:?:
The only difference with the beads was the removal of the red cord they were originally strung on. Hit the cord with a UV light and it glowed electric hot pink.

Ok, starting from the beginning.
Corrections.
Refractive Index: 1.78 (yesterday I used 1.78 RI liquid; today 1.81)
Magnetic Response: Rare earth magnet picks up individual beads....the strand doesn't move.

Color change YES, Reverse color change:NO.
A handful of beads in the dining room:
Image

The same group lit with a fluorescent back light:
Image

Long story short, Stefan tell Dr. Schmetzer, "Nevermind" :oops:

I took my leftover loose beads down to the lab. One bead had a honeycomb like inclusion:
Image

Seen that before?


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 Post subject: Re: Color change pyralspite beads
PostPosted: Sun Mar 18, 2018 2:59 am 
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so high in spessartite with some Goldmanite, Uvarovite and Pyrop...

But you love bug juice colors!! :smt043 :smt044

----

Unfortunately so many use LED to demonstrate a fine blue or more dramatic CC in some spinel or blue sapphire or LW UV to show the quality of pink, orangepink etc. spinel or corundum - course they all fluorescence like crazy - need a lot of iron to quench it.

So exact light source is really important to know...

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 Post subject: Re: Color change pyralspite beads
PostPosted: Sun Mar 18, 2018 12:19 pm 
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Yes. You are right.
I still like my spessartite, goldmanite, uvarovite/ pyrope beads.

The seller said they are from Africa....Stefan, can you narrow it down a bit?

A little research found an older article by Dr. Schmetzer entitled Two Notable Color Change Garnets from Tanzania.

Hhmmm properties seem somewhat similar.


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 Post subject: Re: Color change pyralspite beads
PostPosted: Sun Mar 18, 2018 2:22 pm 
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https://gem-a.com/images/Documents/JoG/ ... 31_5-8.pdf

Here you find the best article about CCG - Madagascar but the same for eastafrican and Sri Lanka material.

They cut many in Bangkok and many dealer from Sri Lanka buy in East Africa so impossible to say exactly which orign...

Multicolorgems offers CCG with orign - Bekily, Nandagala, Taita Taveta...

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