New Mineral Named After GIA’s John Koivula
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 Post subject: photo of clean stones...
PostPosted: Wed Sep 12, 2018 4:43 am 
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was looking at this pic and noticed the baskets that are holding the 2 stones on the left, a tourmaline and sapphire, are clean enough to see the frame through the stones-neat.- :shock: 8)


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 Post subject: Re: photo of clean stones...
PostPosted: Wed Sep 12, 2018 11:01 am 
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... Which just means that the stones have a comparatively low RI and/or are poorly cut ! :P


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 Post subject: Re: photo of clean stones...
PostPosted: Wed Sep 12, 2018 12:02 pm 
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Yes, RI is playing a part, but tone and tilt angle are probably the main contributors. Yes, the stones are nice and clean. Clean stones do look better.


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 Post subject: Re: photo of clean stones...
PostPosted: Wed Sep 12, 2018 12:41 pm 
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Hi, Steve 302!
Review the chapter in Secrets of the Gem Trade, Rethinking the 4 C's.

Here are a couple videos by John Dyer explaining his angle on the subject.





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 Post subject: Re: photo of clean stones...
PostPosted: Wed Sep 12, 2018 2:07 pm 
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When the pic was shot, i was showing a side pic of the framework, the pend was tilted just right to photo through to see the basket on both stones, a benefit of a better camera, dont see how RI would be affected by cut, the cut on both stones is very good & uniform with good polish on both stones, Barbra, thanks for the info, ](*,) 8)


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 Post subject: Re: photo of clean stones...
PostPosted: Wed Sep 12, 2018 5:09 pm 
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ruby302 wrote:
dont see how RI would be affected by cut,

No you don't, do you ?


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 Post subject: Re: photo of clean stones...
PostPosted: Wed Sep 12, 2018 6:42 pm 
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It's the other way around, Steve302...... :smt112

The angles used to maximize light return of a gem mineral are determined by a gem's refractive index and critical angle.

This varies for most all gems. Therefore, ideal proportions will vary for each gem as well.
Make sense?

See this list
http://www.gemcutter.com/angles.htm
Courtesy of the Facet Shoppe- John and Barbara Franke


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 Post subject: Re: photo of clean stones...
PostPosted: Wed Sep 12, 2018 7:22 pm 
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ruby302 wrote:
dont see how RI would be affected by cut ](*,) 8)


There is this thing called critical angle that is directly a function of R.I.. It is an essential property to determining the quality of the cut. Things like polish a a property of finish, which is different.


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 Post subject: Re: photo of clean stones...
PostPosted: Wed Sep 12, 2018 8:26 pm 
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Since we are talking quality, cut, clear, ive got to post the the topaz & tourmaline-pendents are clean, the lines seen on the stones in the center are actually focused from the top of the stone through the gem to the bottom, these stones are flawless & the pics can only show so much, almost as clear as a water sample but with facets- 8)


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 Post subject: Re: photo of clean stones...
PostPosted: Wed Sep 12, 2018 9:44 pm 
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After reviewing the Dyer videos, what do you think of the bi-color tourmaline cut?
Clarity is important, but not the only quality factor for grading colored stones.


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 Post subject: Re: photo of clean stones...
PostPosted: Thu Sep 13, 2018 5:50 am 
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i think the video was very good in that it points out the ideal cut, clarity, & how the gem/diamond should be presented, when i bought the 2 stones, not together, i was given the history of the cuttings, & was shown the 2 cutting wheels, computer controlled, that were used by 2 very experienced cutters, a treat that was. My opinion on both stones is that they were cut/polished to a very high degree, not perfect maybe but very well presented-many appraisers agree, not to mention a few offers on the pendent. Am posting pics of the fire opal, another great cut & at 4.15cts, presents well-[sorry for the dust on the stone]- :roll: 8)


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 Post subject: Re: photo of clean stones...
PostPosted: Thu Sep 13, 2018 12:38 pm 
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I give up.
:roll:


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 Post subject: Re: photo of clean stones...
PostPosted: Thu Sep 13, 2018 2:48 pm 
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No more pictures, the topaz was worn by the wife today & the nurse doing her procedure kept looking at the pendent, serious, asked several questions and offered to buy a similar pendent or this one, no sale, i will give up when the 'dirt nap' does its job. Ur videos gave good info on what to look for in a pristine stone which does not address much of my gems, we are talking $$ for gems from the video. Ur a tuffy, you wont give up too easily =D> =D> 8)


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 Post subject: Re: photo of clean stones...
PostPosted: Thu Sep 13, 2018 10:48 pm 
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Barbra Voltaire wrote:
I give up.
:roll:


Never give up, it's a fascinating study in unique things.... :?


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 Post subject: Re: photo of clean stones...
PostPosted: Fri Sep 14, 2018 2:51 pm 
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I believe that the question was- after watching the Jonn Dyer video, how well do you think the cut is on the bicolor tourmaline? Allow me to answer. The stone is badly windowed with a dead and lifeless center.The ability to see the mounting or newspaper print through the stone is not a good thing. Either all these expert appraisers and gemcutters are wrong or one of the most awarded gemcutters is wrong. I'm going with the clowns that say this is very well cut material.


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