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: Volcanic Opal Scam
PostPosted: Tue Oct 11, 2016 12:40 am 
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This stone just came across my desk. I was told it was Volcanic Opal from Tintenbar in new South Wales. I have dealt with a fair bit of the volcanic Opal from that area and this stone looked nothing like it.

Attached are photos of the 'Opal'. it is resin with foil inside it (Slocum stone). Fairly convincing imitation because it does look like Mexican or Ethiopian opal
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 Post subject: Re: Volcanic Opal Scam
PostPosted: Tue Oct 11, 2016 7:22 am 
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Hello
This is very interesting.
Is the SG of this stone consistent with opal ? Or is it the classical SG of plastic ?


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 Post subject: Re: Volcanic Opal Scam
PostPosted: Tue Oct 11, 2016 6:03 pm 
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The SG sits at about 2.5 while the RI I get is 1.45. Both properties are close to Opal (SG 2ish and RI of 1.45).
Under the microscope there is gas bubbles which also indicates the material is some sort of resin.
Thinking about trying a hot point test to see if it melts

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 Post subject: Re: Volcanic Opal Scam
PostPosted: Tue Oct 11, 2016 6:28 pm 
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Iirc slocum stone is glass, not plastic. Should be easy to distinguish by conductivity and hardness.


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 Post subject: Re: Volcanic Opal Scam
PostPosted: Wed Oct 12, 2016 5:21 pm 
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A SG of 2.5 would be very high for resin (plastic). Bubbles can be found in glass too. The material is more probably glass than resin.


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