'Sea of Glass' in the Bible

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.

And I saw as it were a sea of glass mingled with fire; and them that come off victorious from the beast, and from his image, and from the number of his name, standing by the sea of glass, having harps of God.