December 14-16—SAN DIEGO, CALIFORNIA: Wholesale and retail show; Gem Faire Inc.; Scottish Rite Center, 1895 Camino del Rio S; Fri. 12-6, Sat. 10-6, Sun. 10-5
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 Post subject: Need Advice
PostPosted: Tue Mar 25, 2014 3:34 pm 
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I received this email today. I'm sure you folks can answer this better than I:
Quote:
I have been approached with a business offer to buy a lot of rough rubies from
Pamir in Tajikistan. I’ have spoken to a couple of gem stone cutters in Riga.
They insist that in mountain regions like Pamir, miners use dynamite to break
up country rock in order to reach the ruby rich zone. This method creates micro
fractures inside the rubies, so during the cutting process it could fall to
pieces. Seller insists that they sell gems to Belgium jewelers, who have
equipment that detects amount of these micro fractures. Hence they may estimate
if the gem is good for cutting or not. The question I wanted to ask, does this
sort of equipment exist? Or is there is some other techniques to identify good rough
gems for cutting?


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 Post subject: Re: Need Advice
PostPosted: Tue Mar 25, 2014 4:38 pm 
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Barbra Voltaire wrote:
I received this email today. I'm sure you folks can answer this better than I:
Quote:
I have been approached with a business offer to buy a lot of rough rubies from
Pamir in Tajikistan. I’ have spoken to a couple of gem stone cutters in Riga.
They insist that in mountain regions like Pamir, miners use dynamite to break
up country rock in order to reach the ruby rich zone. This method creates micro
fractures inside the rubies, so during the cutting process it could fall to
pieces. Seller insists that they sell gems to Belgium jewelers, who have
equipment that detects amount of these micro fractures. Hence they may estimate
if the gem is good for cutting or not. The question I wanted to ask, does this
sort of equipment exist? Or is there is some other techniques to identify good rough
gems for cutting?

I know that there's 3D scanning equipment used for diamonds that shows the exact location of all inclusions and the size and shape of cracks, but I don't know what the resolution is or how small of cracks they can detect. I'm sure that you could also use similar equipment to detect internal strain from explosive mining, but this particular described instance sounds a bit suspect.


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 Post subject: Re: Need Advice
PostPosted: Tue Mar 25, 2014 6:10 pm 
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The only method I know of available to most cutters to detect fractures and flaws internally is to use immersion ( refractol or some other High RI fluid ), a light and your eyeballs.

The sellers claim sounds like BS. :P

Edit: I can sometimes see internal strain in a crystal using a polariscope, though.

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 Post subject: Re: Need Advice
PostPosted: Tue Mar 25, 2014 9:51 pm 
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There is equipment that is used to do this, but I have never heard it used for gems. It is used to detect micro fractures in Titanium jet turbine blades. And I don't think it is even close to cheap. Gearloose would know it.

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 Post subject: Re: Need Advice
PostPosted: Wed Mar 26, 2014 4:13 am 
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The dynamite theory is a possibility. I've heard of this being the culprit for fractured emerald. If it is true I'm not sure. However the Chrome atom being what it is I would say it is a possibility.

As far as cutting that emerald went the fractures were easy to see(they certainly were not micro) , even with the naked eye and a bit of light. Naturally a person would select the least damaged to facet. They would not fall apart during cutting but often break during setting or later once set a knock on the stone was sure to break them.

As Wayne mentioned, refractol, light and eyes should be all that is needed, as the description is 'Micro fracture' unless really abundant I think micro fractures are fairly common in stones.

Cutting a window and having a look under the scope with immersion and crossed polars is another possibility.

That all said, get some, facet them and see what happens. Also a method of determining their quality. Call it the acid test.

Regards,

Sean.


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 Post subject: Re: Need Advice
PostPosted: Wed Mar 26, 2014 9:36 am 
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I purchased a parcel of Zircon that had been blasted with dynamite. The stone would often seem to develop fractures whilst cutting. These fractures seemed to grow as I tried to cut them out. Initially I thought it was stress in the stones and they were cracking as the stress was released.

I dipped a stone in a little honey examined one closely before I cut it. The fractures were already there but they were hard to see. They were opening up during the cutting process - which is why the could not be cut out. the fractures had a strange appearance almost like a shadow in the stone. I tried sawing the zircons along the fracture lines prior to cutting. This was successful and I ended up with a finished stone with few problems. However this process often resulted in small odd shaped bits of rough with a low yield. sometimes I would miss a fracture - it was easy to do - as soon as the stone started to crack , that was the end of it. it was a waste of time continuing. I either had to give the fish a new ornament or saw stone along the fracture line if it was large enough to bother with and start again. Some of the stones had too many fractures and literally crumbled during the sawing process.

Ruby is a totally different animal to Zircon so this is probably of no help whatsoever.

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 Post subject: Re: Need Advice
PostPosted: Wed Mar 26, 2014 9:46 am 
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IMHO,,,,,, BS :mrgreen:

Tell the seller to cough up the name of the cutting house and contact them. Junk ruby rough is always a favorite scam of sleazoid rough dealers

Pete

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 Post subject: Re: Need Advice
PostPosted: Wed Mar 26, 2014 1:53 pm 
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 Post subject: Re: Need Advice
PostPosted: Wed Mar 26, 2014 11:49 pm 
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use a laser and eyeball them at 90 degrees or less from the primary beam. Any fractures should twinkle. You could also do this under a microscope, just be careful not to reflect the primary beam into the eye ball and use 5mw or less laser.

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 Post subject: Re: Need Advice
PostPosted: Thu Mar 27, 2014 7:13 am 
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Over the decades I have heard the Dynamite Explanation used for
opal
peridot
turquoise

I suppose there is something to it. Shock waves and crystals or fragile material do not mix.
At present ruby rough is impossible to get. So if someone approached me with some, my opinion would be weighted against the scarcity.

The shock explanation answers the question, "Why, out of billions of people, did this person approach ME, and why does this person have it to offer in the first place?"

Maybe I am old and cynical, with a lifetime full of memories that all say, "You know how this movie ends." :twisted:

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