World Of Gems Conference 2017 Proceedings Book

WORLD OF GEMS CONFERENCE V - 23 - SEPTEMBER 2017 TREASURE FROM TRASH quickly finding what I want to get rid of. Almost all stones that have value are doubly refractive, also it is so simple you can teach a child to do it. I know this to be true because I taught my own child to do it when he was seven years old. What I am looking for are stones with a typical doubly reactive re- action, i.e., the stone blinks light and dark four times in a 360° ro- tation. Figure 4. These are the only stones I keep for further testing. The rest get parcelled to be sold in bulk. If I see anom- alous double refraction, either “writhing snakes” (Figure 5) that indicates glass, “tabby extinc- tion” (Figure 6) which indicates synthetic spinel, or just a general dark reaction, these get pulled. Similarly, anything that remains light is either polycrystalline or heavily included, twinned or filled and likely to not be valu- able. Figure 7. Once I have got all the doubly refractive mate- rial, I then use a conoscope to quickly ascertain the optic sign. Figure 8. You want to see a cross to indicate a uniaxial nature. These are put to one side for a confirmation test and anything with a biaxial figure is sold as a parcel of topaz with a dis- claimer that there may be other stones in there. To confirm the stones are aquamarine, a full RI reading is taken. The principle is the same for all colours. Visually pull out what you can to discard, or that “speaks to you” for further testing, then give it a spin on the polariscope. Sort doubly refractive material by optic character, then carry out confirmation test- ing. For most stones the confirmation test is a full RI reading, red stones usually spectrascope and possibly RI. Any stones offered for sale as single stones will be fully tested and checked under a microscope to ensure they are the right ID, natural and any treatments disclosed, but what this does is efficiently pull out the stones where the money is. You don’t waste time testing stuff you can’t sell, and you can spend time verifying the stuff you can. u FIGuRE 7. Anything that remains light is either polycrystalline or heavily included, twinned or filled and likely to not be valuable. FIGuRE 8. Obtaining an optic sign wtih a conoscope.