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 Post subject: Come Clear Ideas from Cutting an Achroite, Tourmaline.
PostPosted: Sun Jun 26, 2016 2:12 pm 
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Location: Mars PA
When I first saw her on the inter net I knew she had to be mine. She obviously was flawed and had been stained by iron, but her rating was triple A. That meant she had a pure heart and would make a fine addition to my collection. What was this darling's description: A good sized, well shaped piece of Achroite tourmaline rough, that only had one visible problem in the picture on the inter net.. So I was the first to offer her owner the necessary ransom and she flew into my arms.

The water worn chip of about 10 carats did not disappoint me when it arrived. When her turn came up, it was easy to preform into a 10 mm round and the cutting of the culet when without problems. I did push her depth to try and get as large a stone as I could, while duly noting the radial flaw I had left in the part of the rough, that would be fashioned into her crown.

I decided to test out a very well worn 1200 lap to prepare the gemstone for polishing rather than my normal 3000 lap because of the size of the round and the ease of polishing and moving facets that I have found on an Achroite. (She is not the first of my sweethearts) Her mains came in beautifully and then a problem popped up. The lap is so old that it is beginning to shed grit and that means it is toward the end of its useful live. The scratches did not look that bad, but the Achroite turned out to be rather weak and there was subsurface damage that demanded attention.

I polished out the deep scratches by getting off the angle of the facet enough to clearly produce two different parts of the facet. I then work the new facet up close to the scratch. When I am ready, I adjust the polishing angle to be in between the original facet's angle and the newly formed one. With a firm hand I can usually kiss the scratch good by, by polishing the complete facet at the new in between angle. It can be a real effort I may have to repolish a side facet or two. Well she polished so easily that everything worked out until I hit the radial flaw that more or less parallels the nascent table. Now the weakness I had found in the scratches cause the natural flaw to become an open wound. I dropped the crown mains to 35 degrees from 40 degrees and worked the polishing as I did with the scratches. Fortunately i had enough room to work the facet without over polishing it excessively and I finally brought the main home with a flaw that did not mark the facet. (I had to redo the procedure a number of times.)

Now I was rather kicking myself for allowing the flaw to remain in the stone. I could have cut the girdle down a lot or dropped the mains angle some more, but it felt right to cut it as I did. I have become much more tolerant of flaws in tourmaline, when they are handled correctly. In this case the flaw was centered in the middle of a main where a prong could be placed, if it was ever set and it did not extend under the table.

In the end the flaw did not make any difference at all in the stone. She is so bright and flashy that I have not found the flaw by eye, face up. And that is in a pure water white gemstone. Achroite has to be one of the best bargains out there in gemstones. It certainly is rare, but there is such little demand for it that it has a very modest cost associated with really fine material. (When you can find it.) I think that its only real weakness is in having a lower level of dispersion, when compared with other "white" gemstones.

Bruce

Heated material tends to be grayer and duller than the real thing in my opinion. And I would certainly not heat pretty pinks to satisfy my need for Achroite.


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 Post subject: Re: Come Clear Ideas from Cutting an Achroite, Tourmaline.
PostPosted: Tue Jun 28, 2016 5:53 am 
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Joined: Wed Jan 23, 2013 5:29 pm
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Location: Paris
bruce_tourm wrote:
That meant she had a pure heart and would make a fine addition to my collection.


Well, fortunately we know you and what you mean by that ; otherwise that sentence could easily, out of its context, be misinterpreted by your wife (if any). :lol:


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 Post subject: Re: Come Clear Ideas from Cutting an Achroite, Tourmaline.
PostPosted: Tue Jun 28, 2016 8:28 pm 
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Joined: Thu Sep 25, 2008 10:33 am
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Location: Mars PA
Well I know my audience and I am sure that it was crystal clear to them. I compared her with a bigger round that I am sure was (over) heated) in Thailand and the natural Achroite is so much brighter and without a hint of gray. Then I compared the new stone with a really cute emerald cut from my harem of intimate companions and she fit in beautifully.

Bruce


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 Post subject: Re: Come Clear Ideas from Cutting an Achroite, Tourmaline.
PostPosted: Wed Jun 29, 2016 11:14 am 
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Joined: Wed Jan 14, 2015 3:52 pm
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Location: N Dakota
Now that makes for an interesting read. As with most things, when they contain elements that may be provocative or suggestive they tend to hold your attention. The basic information was relayed in an Enjoyable format. Thanks Bruce.

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Dan


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