Help with stone identification

[RRfromR]

What could this be? The seller told me that it tested like sapphire on the presidium, so it could be synthetic. My regular gemologist couldn't tell me because he didn't have a microscope or refractometer, but he couldn't see any gas bubbles. He sent me to another person, who is a gia certified gemologist, the cranky type. He took a look at it and told me it's natural, not synthetic but he'd have to run tests to determine the stone, presidium tester is trash, and he has a 60 people waiting list, he's busy etc etc
The stone has a big window.

 

[T L]

Is it grayish along one of the sides of the stone or in the stone? Like an obvious gray color?

 

[RRfromR]

@T L I don't see a ton of gray

 

[T L]

The circled part looks gray to me, but I don’t see it on the other side.

 

[Daisys and Diamonds]

What could this be? The seller told me that it tested like sapphire on the presidium, so it could be synthetic. My regular gemologist couldn't tell me because he didn't have a microscope or refractometer, but he couldn't see any gas bubbles. He sent me to another person, who is a gia certified gemologist, the cranky type. He took a look at it and told me it's natural, not synthetic but he'd have to run tests to determine the stone, presidium tester is trash, and he has a 60 people waiting list, he's busy etc etc
The stone has a big window.

love thd presence it has on your finger

 

[T L]

If it’s grayish in certain observed directions, I suspect iolite, which has a low refractive index, is typically very clean, and can look a beautiful blue/violet along other axes. However, you just cannot tell from a photo.

It could be synthetic, a simulant, or kyanite.