Identify Unusual Greenish Gemstone

[AntiqueLocket]

This gemstone ring I have looks almost grayish-clear in the house. I was taking photos, and it ranged from very light green to a darker, odd-color green. It may be nothing, but I thought I'd ask the community.
A few months ago, I sold an unknown solitaire for under $100.
After the buyer received it, they said they bought it on a "hunch" and believed it to be an Alexandrite.
I learned a possibly expensive lesson. They said they would give me a little extra if re-sold, which was extremely generous, but I haven't heard anything and don't expect it. It was very kind for someone to even offer!
Anyhow, I thought I'd see what the pro's opinions were on this green ring. Heck, it could just be the way I had it positioned, but again, I didn't want to make another mistake if I can help it!



I have a gemstone tester, but am not knowledgeable enough on the subject. It isn't glass, I do know that much!
I like to lurk and learn on this forum/website, and there's so much fabulous info out there!

 

[T L]

Looks like a prasiolite, or green quartz.

 

[minousbijoux]

Second that. It is common for gemstones to display color variation and to shift color depending upon the strength and type of light.

 

[stracci2000]

Could it be uranium or Vaseline glass? Synthetic spinel? I understand that synthetic spinel tests the same as natural. Someone may correct me on this.
We've had some threads on yellowish-green mystery stones lately.
.

 

[tigertales]

fossilized alien eyes.

just kidding.

could also be a very pale green sapphire. the texture and cut remind me of the pale "white"/blue sapphires

 

[lovedogs]

There is almost zero chance it is alexandrite. My guess is synthetic spinel, or quartz.