'Sea of Glass' in the Bible

and before the throne there was as it were a sea of glass like to crystal; and in the middle before the throne, and around the throne, were four living creatures full of eyes before and behind.

And I saw as it were a sea of glass mingled with fire, and those who had gained the victory over the beast, and over his image, and over the number of his name, standing at the sea of glass, having harps of God.