I am scratching my head over a gift, from half way around the World!

My Sister and I are rock hounds and we both love gemstones in particular. She retired from head buyer at Hobby Lobby, which included a lot of World travel. She 'adopted' an extra Son in Turkey, who ran a yarn factory; who has come to visit her several times.

She read about some agate mined in Turkey that is reported to be stunning, so when he wanted to send her a present; she asked for some. He went to the grand Bazaar, and bought one for her; and because he knew I was fond of rocks too, one for me.

This is what he sent:

The flash on my camera is very close to natural sunlight, but it washed out some of the color saturation. The purple is significantly darker, like a high grade amethyst. So I decided to turn off the flash, and use room lighting to try to draw out the color. That's when things went crazy....

Like this:

This rock is dichromatic, showing two different colors under different light sources, in this case tungsten! This means this is crystalline, otherwise called a gemstone....

Since it is 9 inches in diameter, an over an inch thick; this is a significant piece of material!

I have no way of examining the crystal shape, so that won't help identify it. I will measure the refractive index, the mho Hardness, see if I can get any internal crystal angle information with my dicroscope; and test the spectrum with my spectroscope. The saturation is too dark to gain much from my microscope.

Anyone have any other non destructive tests I can do? If I cut off a piece, I could do specific gravity.

Without any other testing, this is a real possibility:
https://www.gia.edu/alexandrite
The colors look close on the rectangular stones here. If it turns out to be Alexandrite, it would be worth a fortune!

What a fun present! It will take me months of testing to I.D. this stone...if I'm lucky!