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Identification of Clear High-RI crystal https://www.gemologyonline.com/Forum/phpBB2/viewtopic.php?f=24&t=25212 |
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Author: | gembug [ Mon Jun 03, 2019 5:33 pm ] |
Post subject: | Identification of Clear High-RI crystal |
I have a boule end of a pulled synthetic on its way to me, but of unknown composition. I'm told the material in question has a density of ~4.2-4.4 but that's all the information I have. Any suggestions of other tests to do that might help narrow down the candidates? The RI is well over 1.8 so my refractometer won't be much help. Thanks! -Allan |
Author: | cascaillou [ Fri Sep 06, 2019 9:22 pm ] |
Post subject: | Re: Identification of Clear High-RI crystal |
Let's just start with classical gemological testing: -observation of surface features and inclusions under magnification (loupe/microscope) -in the process, also check for doubling (of broken angles, inclusions and/or surface features), -confirm exact SG of the material, with two decimals (let's note that a digital scale accurate to 0.01g will work fine provided that the stone weighs at least 3g), -give a few tries at a spot reading with the refractometer, just to confirm that the material is indeed unreadable (I know it is supposed to be >1.78 and thus unreadable but let's just make sure) -then see if you can try and get the optical character of the material using polariscope+conoscope (note that a polariscope can be built from a broken LCD screen, and a triplet loupe can be used as a conoscope). -check spectrum (if any) with handheld spectroscope -check LW & SW UV fluorescence (if any) -considering it's a rough, you may also want to check hardness (first try against a plate of copper, if copper gets scratched then try against glass, and if glass gets scratched then try against a polished piece of quartz). Oh and don't forget to provide us with a clean picture (properly focused, in daylight, over a white background) |
Author: | Barbra Voltaire, FGG [ Sat Sep 07, 2019 8:47 pm ] |
Post subject: | Re: Identification of Clear High-RI crystal |
Or, if push come to shove, knock off a wee bit and send it to me. I'll give it a spin on the GemmoRaman. |
Author: | gembug [ Sun Sep 08, 2019 12:43 am ] |
Post subject: | Re: Identification of Clear High-RI crystal |
Thanks for the ideas. SG was about 4.5 LWUV reaction - weak pink fluorescence Not able to get SG reading at all - even polished a little flat on it. So above 1.8 No reaction in polariscope After putting all this together, I came to the conclusion it's clear YAG. Too bad, I was hoping that it was Lithium Niobate But clear YAG isn't so bad also. -Allan |
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