Most likely a synthetic color change sapphire. Look for RI of 1.76 to 1.77 DR.
I would agree with mhutton. A synthetic color change sapphire.
An alternative possibility is that the specimen is Zandrite, which is a copyrighted name for synthetic Alexandrite sold by JTV.
Thank you for your comments and i will stop using steel tweezers.
I haven’t any idea what the stone is but the cut was done to get the most carat weight. A good cut would not allow you to see through it.