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 Post subject: A $45/ct Knischka Lab-Grown Ruby Rough
PostPosted: Mon Jul 27, 2009 1:11 pm 
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Lab-grown ruby rough usually costs 15-25 cents/ct. The most expensive I have seen is $1.25/c.

This lab-grown rough is, the description suggests, related to Paul Otto Knischka who is a pioneer in the growing of ruby crystals. Who is Paul Otto Knischka? Does “Knischka Lab-Grown” justify the price?

Please enlighten me.

Mitch

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PostPosted: Mon Jul 27, 2009 1:26 pm 
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The Knischka synthetics were legendary in their time.
I haven't heard the name in years.
When I was a student in Germany, there was a famous story about a faceted Knischka ruby being presented to DGemG for identification.
It ended up at the University of Heidelberg for study as the DGemG results were inconclusive.
It was determined, after much ado, that the Knischka was synthetic because it lacked any gallium. All natural rubies studied contained a ppm trace amount of gallium.
The gem was given back to Knischka with a detailed report on how "Synthetic" was determined.
His response:
"Next time I'll add gallium."


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PostPosted: Mon Jul 27, 2009 1:54 pm 
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I would be leery of that seller! I dealt with them before. Purchased a supposed synthetic zircon crystal(which they still have for sale!!). It turned out to be nothing more then a synthetic spinel! I contacted them with no answers at all and they still have not bothered to change the auction description yet either! I personally would not trust their descriptions!


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PostPosted: Mon Jul 27, 2009 2:37 pm 
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How did you determine it was synthetic spinel?

I purchased a hackmanite sphere from them several years ago and it properly represented. I found them to be forthcoming and very willing to share information.


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PostPosted: Mon Jul 27, 2009 2:47 pm 
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Thanks, Ms Barbra and Swishman,

So if this rough is truly a Knischka rough, it may be valuable to the collectors who know and appreciate the Knischka rough. Is this price appropriate? Is there any way to tell the Knischka rough from the other lab-grown ruby?

Has Prof. Knischka eventually made the gallium-containing rough?

Mitch

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PostPosted: Mon Jul 27, 2009 2:52 pm 
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mhuynh wrote:
Thanks, Ms Barbra and Swishman,

So if this rough is truly a Knischka rough, it may be valuable to the collectors who know and appreciate the Knischka rough. Is this price appropriate? Is there any way to tell the Knischka rough from the other lab-grown ruby?

Has Prof. Knischka eventually made the gallium-containing rough?

Mitch


I don't know. I heard the story in 1984 and have never followed up. :lol:


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PostPosted: Mon Jul 27, 2009 5:51 pm 
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Barbra Voltaire wrote:
How did you determine it was synthetic spinel?

Sent into a school for more high end testing as well. It is 110% NOT zircon, but a common syn. Spinel crystal. Buy one and check for yourself. :(. I gave both mine to the school, but I am sure I can get a list of testing done on it by them if you desire. I have plenty of close up and higher magnification images of them if you want me to post them or send them to you I can.

I would not have been so upset had they even bothered to reply to my correspondence but I never even got so much as a reply more or less reason/apology. Not good biz practice imho.


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PostPosted: Mon Jul 27, 2009 8:47 pm 
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It's a little less than $20/ct, 45ct rough


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PostPosted: Mon Jul 27, 2009 11:17 pm 
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Oh, I see “Rough Crystal @ 45.00 cts.” means the size of the crystal is 45 cts. So $875/45 cts. = $19.44/ct. It is still about 100 x more expensive than regular lab-grown ruby rough.

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PostPosted: Mon Jul 27, 2009 11:18 pm 
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Here are a few of the pics Barbra:
Image
Image
Image
Image
Image


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PostPosted: Mon Jul 27, 2009 11:22 pm 
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Gorgeous shots, as usual, Mr. Man.....but :oops: what are they the pics of?


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PostPosted: Tue Jul 28, 2009 12:00 am 
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Barbra Voltaire wrote:
Gorgeous shots, as usual, Mr. Man.....but :oops: what are they the pics of?

Thx, they are pics of the Syn. Spinel crystal sold as the Syn. Zircon.


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PostPosted: Tue Jul 28, 2009 12:25 am 
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Oh...well.
I would have called in the big guns for this ID too.


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PostPosted: Tue Jul 28, 2009 1:00 am 
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At the time I had no choice either as I was bed ridden and unable to do any tests on my own, lol. But I also wanted a "beyond a doubt" ID as well.


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PostPosted: Tue Jul 28, 2009 2:37 am 
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what is being sold is not just synthetic corundum but a piece of history, along with that company's pretensions - referring to their "collection", for example. knischka's stone, according to my well-thumbed copy of o'donoghue (synthetic, imitation and treated gemstones) is detectable only thru internal examination which would show "metallic black platelets and two-phase inclusions with prominent gas bubbles and long tubes ending in negative crystals" . bright multifaceted crystals not attached to matrix should raise suspicions. . . if you look at the pictue you will see just how bright those facets are.

a challenge to swishman and every other member who rails against ebay on this forum:

if you know that a seller is peddling any sort of fakery, report him or her! even if it does not seem to be productive at first you will make a difference because an onslaught of reports means ebay staff must take time to sort thru the reports, and time is money.


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