Light blue stone, need ld

[Shiny Black Cat]

Hello l need help id, please. I don't know what to think about this ring. There are some markings which I can't decipher because they are worn off. The stone is light blue, green, sometimes pink, depends on lighting. Maybe someone has something similar? Thanks for any info.

 

[LemonMoonLex]

Reminds me of diaspore but could also be something synthetic as it looks huge, fairly clean, & the setting looks worn. Excuse me as I cannot see the stamps well but is it set in gold, silver, or brass and nickel? It's hard to tell.