New Mineral Named After GIA’s John Koivula
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 Post subject: Cordierite aka by the trade name Iolite: rough
PostPosted: Tue May 21, 2019 10:23 pm 
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"Iolite"

Edit:

Just over 560grams rough crystal gemmy quality museum piece.

Stone: Cordierite aka by the trade name Iolite: rough
Colour: Dark blue, Blue, Greyish blue, Greyish Purple, Greyish yellow.
Refractive Index: 1.542 - 1.551
Relative Density: 2.53 - 2.65.
Hardness: 7 - 7.5.
Crystal group: Orthorhombic.
Tenacity: Brittle.
Origen: Africa - Tanzania.
Mined: 2018.



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Last edited by offimatrix on Wed Jul 17, 2019 12:11 pm, edited 2 times in total.

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 Post subject: Re: Iolite routh
PostPosted: Wed May 22, 2019 11:58 am 
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While we appreciate the pictures you are posting, please remember this is an educational platform.
Include information about your specimens. The pictures, on their own, tell us very little.
Thanks for understanding.


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 Post subject: Re: Iolite routh
PostPosted: Wed May 22, 2019 12:34 pm 
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Barbra Voltaire wrote:
While we appreciate the pictures you are posting, please remember this is an educational platform.
Include information about your specimens. The pictures, on their own, tell us very little.
Thanks for understanding.


Sorry for anything i'm missing out. I'm new here and getting use to how forum works also my pc spell checks at times as soon as I post. There also is a lot on here to catch up on.

Iolite is also from Tanzania, Name of Mine is unknown but mined in 2018, Sorry again if i'm missing bits out.

Specimens I have don't have there size recorded, Only Weight Origin and Stone name and Crystal grade.


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 Post subject: Re: Cordierite aka by the trade name Iolite: rough
PostPosted: Tue Jun 04, 2019 10:38 am 
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Stone: Cordierite aka by the trade name Iolite rough crystal shard.
Colour: Dark blue, Blue, Greyish blue, Greyish Purple, Greyish yellow.
Refractive Index: 1.542 - 1.551
Relative Density: 2.53 - 2.65.
Hardness: 7 - 7.5.
Crystal group: Orthorhombic.
Tenacity: Brittle.
Origen: Africa - Tanzania.
Mined: 2018.

Weight: 200grams. 1000cts.
Size: 102,5 x 44,5 x 38,5

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Last edited by offimatrix on Wed Jul 17, 2019 12:11 pm, edited 1 time in total.

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 Post subject: Re: Cordierite aka by the trade name Iolite: rough
PostPosted: Tue Jul 16, 2019 4:37 pm 
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Stone: Cordierite aka by the trade name Iolite rough crystal like spear head.
Colour: Dark blue, Blue, Greyish blue, Greyish Purple, Greyish yellow.
Refractive Index: 1.542 - 1.551
Relative Density: 2.53 - 2.65.
Hardness: 7 - 7.5.
Crystal group: Orthorhombic.
Tenacity: Brittle.
Origen: Africa - Tanzania.
Mined: 2018.

Weight: 102grams. 510cts.
Size: 69,3 x 49,3 x 27,1
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All 3 together.
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Last edited by offimatrix on Wed Jul 17, 2019 12:11 pm, edited 1 time in total.

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 Post subject: Re: Cordierite aka by the trade name Iolite: rough
PostPosted: Tue Jul 16, 2019 6:54 pm 
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Your refractive index is wrong. it should be 1.596 - 1.522.


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 Post subject: Re: Cordierite aka by the trade name Iolite: rough
PostPosted: Wed Jul 17, 2019 1:28 am 
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A Google check gets numbers all over the place...

GIA - 1.542 - 1.551

Wiki - nα = 1.527 - 1.560 nβ = 1.532 - 1.574 nγ = 1.538 - 1.578 (Indices increase with Fe content._)

Gemology Online - 1.542-1.551

Gemdat - 1.542 to 1.578

Also, Manual of Mineralogy (Hurlbut & Klein) - 1.522-1.573

Don't see any as high as 1.596. Reference?

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 Post subject: Re: Cordierite aka by the trade name Iolite: rough
PostPosted: Wed Jul 17, 2019 6:30 am 
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I'll keep with the 1.5 varies.
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 Post subject: Re: Cordierite aka by the trade name Iolite: rough
PostPosted: Wed Jul 17, 2019 8:35 am 
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Just looked up the RI for Iolite in my Gem Tools Pro database. GTP tends to show the RI range with the variances built in. Basically showing the lowest, and highest being reported by different sources. This makes sure that your readings should be in the range. It also matches your findings.

GIA lab manual has 1.542 - 1.551 (+0.045/-0.011) which matches on the high side, and is slightly different on the low side.

I can't find any source for 1.500.


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 Post subject: Re: Cordierite aka by the trade name Iolite: rough
PostPosted: Wed Jul 17, 2019 12:09 pm 
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1bwana1 wrote:
Just looked up the RI for Iolite in my Gem Tools Pro database. GTP tends to show the RI range with the variances built in. Basically showing the lowest, and highest being reported by different sources. This makes sure that your readings should be in the range. It also matches your findings.

GIA lab manual has 1.542 - 1.551 (+0.045/-0.011) which matches on the high side, and is slightly different on the low side.

I can't find any source for 1.500.


1.5 with the end bit missing means it varies, I don't have tools double check stones and google
searchers as abeck says are all over place.

I'll put iindex to what says GIA - 1.542 - 1.551


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 Post subject: Re: Cordierite aka by the trade name Iolite: rough
PostPosted: Wed Jul 17, 2019 12:50 pm 
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When the RI of a mineral shows this much variation, remember the birefringence should remain fairly constant.
Birefringence: 0.008 - 0.012


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 Post subject: Re: Cordierite aka by the trade name Iolite: rough
PostPosted: Wed Jul 17, 2019 8:19 pm 
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Barbra Voltaire wrote:
When the RI of a mineral shows this much variation, remember the birefringence should remain fairly constant.
Birefringence: 0.008 - 0.012


Birefringence is the most constant and dependable property in gemmology if I remember correctly.


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