Help to confirm identity of this

I recently obtained this reasonably large 9ct gold ring, with a baguette cut gem. Its incredibly clean inside, can’t identify any faults apart from a few fine/soft surface scuffs. Under UV light in normal conditions it turns a lovely crimson red. In normal conditions its a dark blue, with subtle purple shades. My comparison tests rule out Amethyst. So without hinting to anyone on the group - and as a newbie gem appreciator - could anyone help with its identification? Please? Many thanks.

It could potentially be glass. What is the RI?


My impression from your photos is Laboratory Created Spinel. The cut of this stone is Octagonal Step Cut (Baguettes have 90 degree corners). It would be like calling a Radiant Cut a Princess Cut.


To my opinion synthetic spinel. Has red fluorescence under LW


With the stone being as clean as it is, it is most likely synthetic.
Synthetic violet sapphires glow strong red in LW and green-blue in SW.

however Natural cannot be ruled out without further testing.
Some Sri Lanken sapphires can fluoresce red to orange under LW and light blue under shortwave.

That particular color of red florescence makes me think the stone contains chromium impurities.
Try looking at it with a Chelsea filter. It should look red if it has chromium.
Note: Stones that get their blue color from cobalt may also appear red through a chelsea filter.

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Typically when gems do this under UV it is a pretty good sign of heating and or Synthetic. But you need the RI, Specific Gravity and hardness and possibly even the Spectrum Fingerprint to know for certain.
-Mike at Acquire Collectibles Gemological Laboratory Services