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Why is there rainbow color on the table of a gem?

Is it normal to have the rainbow (oil like) color on the table of an emerald? I have a red spinel that shows this as well… any explanation would be appreciated.

I mean - most Emeralds are oiled…maybe there is an excess of this substance?

Hi Jessie,

please take it out of the box and have a look if it has the rainbow.
Due to the pressure from the Stone touching the glass there could be a rainbow effect.



The very thin space between the glass and the table of the gemstone causes rainbow-like interference colors in the same way very thin fractures do inside transparent minerals.

This could be an indication that you have a doublet … tripet… Soude emerald… More testing would be needed. But you’re likely seeing an interference image … could have glass . Or could be garnet topped… Hope that helps

Thanks everybody for your replies. I checked, it was really the glass on top of the stone that’s creating the rainbow effect! Something new I learned. Appreciate the help!

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