One of the most difficult and common things in today’s Gem and Jewellery business is to detect Synthetic from Natural Spinels. How to find it for buyers of Natursl spinels to make sure they are not buying the wrong gemstones.
The RI is often a little higher, but not every time
The composition is not exactly the same, but I can’t analyze it. Maybe a spectrometer could be helpful
I prefer to buy slightly included stones, preferably rough, and identify natural inclusions. So so beautiful anyway
Long wave UV light makes synthetics glow strongly and lines of small gas bubbles, often curved are another sign. Flux inclusions and curved growth lines might show with good magnification.
Green spinel is rare so careful buying one. Blue spinel is a common one to synthesise
Both the above, and also the presence of crosshatching in the crystal under magnification.
But your right, this can be a tough one, and the blue colours seem to be the most commonly found synthetics.