And over the head of the living creature there was the likeness of a firmament, like the terrible crystal to look upon, stretched forth over their heads above.

and before the throne, as it were a sea of glass like a crystal; and in the midst of the throne, and round about the throne, four living creatures full of eyes before and behind.

having the glory of God: her light was like unto a stone most precious, as it were a jasper stone, clear as crystal: