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 Post subject: Re: Tourmaline
PostPosted: Wed Apr 07, 2021 11:31 pm 
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glhays wrote:
mehoose wrote:
So, after side stepping the aforementioned dung :smt077 ... I did manage to unearth a few references in here and they allude to Toums being pyroelectric and piezoelectric...so not quite a pipe but... :smt025 :smt116

A quick read here(thank you ClassyCarat)
viewtopic.php?f=21&t=1169&hilit=pyroelectric
and here
https://www.gemologyonline.com/Forum/phpBB2/viewtopic.php?f=8&t=19370&p=194931&hilit=pyroelectric#p194931

I know there were more smattered throughout threads over the years but you'd have to try different searches.
It was just something I'd made a mental note of because there were some beautiful Tourms being cut and one I'd love to cut myself one day. I remember tourms were and probably still are x'y and I'd have to take greater care with so I wasn't just flushing the $ away.


Ok let me see if I can dig my self out of this dung hole I got myself into.
I never have been a good dancer that I know of, maybe in age I have acquired some steps or two, not very good by the looks of things.

I apologize to you and Happy Cow completely to suggest you were leaving behind a trail of Dung Beatles favorite past-time, I love getting licked across the face on every post you make by happy cow icon, it cheers up the thread where ever it appears. It is a cow right? :?

I will be researching this polarized tourmaline not just here but in our collection of old magazines and literature. Not to prove anything, but just from curiosity.
Have a great day over there and cheers to you and yours. I am very sorry for the implied. :-#
Greg



:lol: :smt046 It's all good! :smt056 Yes, that teeny pink think is an udder if you blow the page up big enough. I'm a bit of a stirrer myself, rely heavily on emotis in those instances to cross language divide so folk know when I'm kidding....Of course that all goes out the window if someone has disabled them.. but I don't set out to hurt or belittle...and I ALWAYS have to remember to never shorten the word 'computer' on GO. :oops:

Back to the Tourm quirks.
Mind you, my machine doesn't have a reverse switch so I could still be up that creek when it comes time to cut my first one. :roll:

Would definitely appreciate being set straight on the inference I came across of not to use water when cutting/polishing Tourms.

I'm back and I'm here to start all over again...like a complete noob..... with a few wee gems locked inside from eons past, waiting to fall out at the appropriate moment to shine their light on something.

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Most of the fire on the wall has been put out :)


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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 10:32 am 
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Done. Hard to get pics, kinda dark but super flashy. I like it.


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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 10:36 am 
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Before and during. Started 8.7ct end 1.3ct was a weird nodule shape but maybe I could have done better.


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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 10:38 am 
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What's a good crown angle for the dark stuff? Mine is 39/41 pav then 21 crown.


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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 1:48 pm 
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I do not believe angle on that particular rough would have helped. You can try steeper pavilion girdle facets and lower the crown mains to say 35 degrees. Will introduce some more light into the stone. The darkening is more than likely the closed c-axis being reflected and or refracted within the stone.

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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 2:53 pm 
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Ok I'll try that on the next closed piece. This one is considerably lighter, has a nice aqua ab color and green c. Open on this.


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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 3:04 pm 
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Maybe people don't like the darker stones but I love it. The contrast between the dark and yellow/green is really cool looking to me. I'm excited to see the color on the next one though.


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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 3:46 pm 
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Yes all part of personal preference when it comes to color, cut, brilliance, dispersion and more.

Take a moment and look at the image of the 5.85ct. rough on the scale, see the black or dark green on the end closest to the viewer. That is what your dealing with it is staring you in the eye, one end is transparent and other is not in some degree. based on the shape of the rough you will probably cut it in the orientation it is laying on the scale to maximize weight (just an assumption here). But if you go back to the window with natural light it appears to be a very transparent gem throughout, mainly because your looking at it in it's best light per say. Lay it on a white sheet of paper just the way you have it laying on scale with the window light as a backlight and look at in the same view as the scale image, if you still see half the stone darker than the other, that half is going to give you a dark low life stone most likely.
Just offering some helpful information, not trying to be critical in any way.

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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 3:51 pm 
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j.mcgee_1985 wrote:
What's a good crown angle for the dark stuff? Mine is 39/41 pav then 21 crown.

21 crown means what breaks, mains, stars? It looks like the crown is faceted in a step design?

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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 4:29 pm 
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Mains, single cut on the crown. The bottom is fancy but it's very hard to tell, I might do the opposite on the next dark stone. Fancy top simple bottom.


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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 4:46 pm 
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glhays wrote:
Yes all part of personal preference when it comes to color, cut, brilliance, dispersion and more.

Take a moment and look at the image of the 5.85ct. rough on the scale, see the black or dark green on the end closest to the viewer. That is what your dealing with it is staring you in the eye, one end is transparent and other is not in some degree. based on the shape of the rough you will probably cut it in the orientation it is laying on the scale to maximize weight (just an assumption here). But if you go back to the window with natural light it appears to be a very transparent gem throughout, mainly because your looking at it in it's best light per say. Lay it on a white sheet of paper just the way you have it laying on scale with the window light as a backlight and look at in the same view as the scale image, if you still see half the stone darker than the other, that half is going to give you a dark low life stone most likely.
Just offering some helpful information, not trying to be critical in any way.


I'm glad you pointed that out. In the picture it is dark but when I'm holding it it doesn't seem closed at all. I was going to cut the table on the first picture. It's hard to tell but it tapers on 1 side. If I don't put the taper down (pav side) I don't think I'd have enough depth any other way. I see what your saying about the c being partly closed now. I think I'm using too much light to judge how closed it is. When I did what you said it looks partly closed now. Thanks!


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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 5:20 pm 
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Okay got it! Wasn't looking close enough to the images. Not much you can do with a 21 degree and a table other than go lower or just cut a flat table across it.

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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 5:49 pm 
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Ok, I'll try something like 45-48 deg on the pav next and 33 - 35 deg on the crown.


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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 6:59 pm 
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j.mcgee_1985 wrote:
Ok, I'll try something like 45-48 deg on the pav next and 33 - 35 deg on the crown.

Try changing your 39 to 41 & the 41 to say 46 or 48, then on the crown if your sticking to this same design do one row of 38, and another row of 32 or 33, another row of 21 then cut in a table make the crown a step cut. That is if your going with octagonal shape.

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 Post subject: Re: Tourmaline
PostPosted: Thu Apr 08, 2021 10:43 pm 
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Dark stones look better with fewer, larger facets. Since the amount of color absorbed is directly related to the length of line the light travels inside the stone the goal is to shorten the line.

Do a simple step cut on both crown and pavilion. Sometimes it is best to let light leak. Transmitted light travels the shortest possible path.

Over time you will develop a library of cuts that work well for dark stones.

As I have said, you need a consistant way to evaluate your rough. I will have a new batch of light boxes finished next week.


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