Hello. I have a turquoise ring with a spiderweb stone that I would like to identify. The first photo is in direct sunlight and the 2nd darker photo is inside, with no light. It’s a dark stone, but really comes to life in sunlight. There are so many different mines that produce spiderweb stones. The blue on this is really electric. Any help would be appreciated. It’s signed on the back with a date 4-75 and the artist or owner’s intial’s REN Thank you.