The wall was made of jasper, and the city itself of pure gold, as pure as glass.

Revelation 4:6
And before the throne was something like a sea of glass, as clear as crystal. In the center, around the throne, were four living creatures, covered with eyes in front and back.

Revelation 21:11
shining with the glory of God. Its radiance was like a most precious jewel, like a jasper, as clear as crystal.

Revelation 21:21
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.

And the building of the wall of it was of jasper: and the city was pure gold, like to clear glass.