Fake Gemstone Report And A Little Yellow Sapphire

Fake Gemstone Report And A Little Yellow Sapphire

Every now and then I come across something that shocks me. This is one of those cases. I had a Yellow Sapphire come across my desk recently and right from the onset I thought something wasn’t right. The customer had bought it off the internet and wanted me to check it out for authenticity. It came packaged in a nice box with a gemstone report from a gemologist who had tested it. I never look at gemstone reports before testing so that my mind is completely clear. I don’t want anything to sway my decision so I base my findings purely on results. Time to start doing some test.

Visual Tests

These are tests that can be done without any specialist equipment In most cases all that is needed is your eyes and sometimes maybe a loupe. So this stone was poorly cut, nothing surprising there. It had a strange colour to it, something that I would not expect from a yellow Sapphire. It was obvious that by rotating the stone, the colour was mostly coming from the bottom of the stone and being reflected around. Usually the colour comes from inside the stone and rotating it does not change the colour of the stone.

Under The microscope

This is always the fun part where you get to see up close what is really going on. The first thing I notice is the inclusions inside the stone. Plenty of liquid filed tubes inside of the stone which had my questioning straight away the flase gemstone report which says Sapphire. Liquid filled tubes are classic inclusions inside gems that form inside pegmatites (Beryl, Topaz, Quartz). Could the fake gemstone report really get it so wrong.

Next up I start to look over the stone for any traces of anything else suspicious. On the bottom of the stone I find some yellow residue of what looks like dye. It is obvious that most of the dye has rubbed off and only small amounts remain This is what is giving this stone the yellow colour.

Testing Refractive Index (RI)

This is the nail in the coffin. Each mineral has it’s own refractive index that is unique. It is one of the main ways that gemologists differentiate between minerals. I place some liquid on the refractive index reader and place the gemstone on top. To my surprise the RI of this gem is 1.61 – 1.62. The RI of Sapphire is 1.76 – 1.77 so there is no way this could be Sapphire. Again could the fake gemstone report really get it so wrong. There is only one gemstone who’s RI fits the bill, and that’s Topaz. It is all falling into place now, the RI is telling me it is Topaz, the inclusions are telling me it is a stone formed in a pegmatite such as Topaz and it is dyed yellow.

Removing The Colouring

Just to be sure that I am correct, I place the stone in some acetone. I use standard nail polish remover as this will remove anything that is coated onto the stone. I also want to remove the coating so I can take the RI reading again just in case the coating is interfering with the machine.

After a few hours, the acetone has turned yellow and the stone is now clear. I double check the RI and it is still consistent with Topaz.

The Fake Gemstone Report

Lets take a close look at the fake gemstone report.

false gemstone report

  • Lab is called GTLI (Gemstone testing laboratory of India). No website, email or contact details are on the report.
  • The weight, dimensions and shape of the stone is correct
  • It is listed as  DR gem (Double refractive), this is correct
  • The RI is listed as 1.76 – 1.77, this is fake. From the tests above the RI of the gem is defiantly consistent with Topaz
  • Species listed as Corundum This is fake, corundum is Sapphire or Ruby.
  • Treatment listed as Hue Enhanced. This is correct as the stone was dyed.


It is unfortunate that this stone had a fake gemstone report because the customer truly believed it was the real deal. It is a very convincing fake gemstone report because it contained so much of the technical information required to correctly identify the stone.

It is essential that customers have confidence on who they are buying gemstones off, especially when they are worth so much money. If you believe you have a stone with a fake gemstone report, I suggest you send it to a reputable lab for a re test so that you have piece of mind.


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