Blue glass/quartz/crystal? 001

I found this piece in the bush many years ago and I still don't know what it actually is. It's about an inch thick 26mm and too heavy and too cold for fiberglass and is beautiful cobalt blue when held up to the light. Personally I think it's volcanic glass! Either way it is a great conversational piece and beautiful to look at. It has a great home in my Bower bird nest.

Done