Immersion test

Hi my colleagues in this educational forum
Could you please tell me which is the best liquid that has reflection index very close to that index of ruby gemstone to do immersion test… The affordable one is the best.

You can use diiodomethane, that is the closest refractive index to ruby, 1.74, ruby being 1.76. But it is spendy. I have used my go to liquid which is wintergreen oil and it never lets me down. Much less expensive and such a nice scent!

Benzyl Benzonate has an RI of 1.568. It is colorless and nontoxic and is used as an immersion liquid my many faceters. There are liquids which are closer in RI to corundum, but most are more toxic or are irritants (e.g., cinnamon oil, RI+1.62, is a skin irritant). The stone’s skin will not entirely disappear in benzyl benzoate, but you will be able to see into the interior very well to see flaws. You can buy benzyl benzoate on ebay. -royjohn

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