Glass

A substance remarkable for its transparency. Two phenomena seen by John in his vision in the book of Revelation are likened to glass.

The sea of glass

Revelation 15:2 See also Revelation 4:2–6

And I saw something like a sea of glass mixed with fire, beside which stood those who had conquered the beast and its image and the number of its name. They were holding harps from God,

The gold in the new Jerusalem likened to glass

Revelation 21:21 See also Revelation 21:15–18

And the twelve gates were twelve pearls, with each gate consisting of a single pearl. The main street of the city was pure gold, as clear as glass.