Ring stone

1) under black light
2) natural outside light
And 3rd) normal natural light

Can anyone tell me why the stone looks like this under the black light?
I'm aware the different types of stones look different but I'm mostly seeing that blue is the color it should be. I am having to use a light that is not working 100% . It's weak. But all I have at the moment. How close should it be held to the light ?
Thanks

 

Dreamin, you already posted the same thread earlier today:
https://www.antiquers.com/threads/ring-stone.25328/
Please look at the answer, and if you want to know more, just ask.

 

Im sorry. I was having a hard time and opened another tab and didn't realise it created twice. Thank you.