Gahnospinel lovers?

I was looking about the Gahnospinel market & value but couldn’t able to find. Highly appreciated if anybody out there can shed some light about the relevant facts.

4.97 carat, Sri Lankan Origin, Violetish Green Blue, Rare Spinel

This can be difficult to identify because it produces a wider range of R.I. and SG. than regular spinels.

True, this stone has 1.725 RI. Where normal spinel has 1.718

Have you seen this on the IGS website?

Seems to cover your question.