'Sea of Glass' in the Bible

And before the throne was a sea of glass, like crystal: and in the middle of the throne, and the circle of it, were four animate beings full of eyes before and behind.

And I saw as it were a sea of glass mingled with fire; and those that had gained the victory from the beast, and from his image, and from his mark, and from the number of his name, standing on the sea of glass, and having harps to celebrate the praises of God.