Revelation 21:18; And the Building of the Wall Was of Jasper

Revelation 21:18 (KJV) And the building of the wall of it was of jasper: and the city was pure gold, like unto clear glass.

The description moves on to speak of the materials which have gone into the city’s construction – And the building of the wall of it was of jasper: and the city was pure gold, like unto clear glass.

Etymologically, the noun “the building” giving the impression that the wall had jasper built into it. Being cased with precious metal, it sparkled with crystalline radiance. In Revelation 4:3 the One sitting on the throne is like jasper, and in Revelation 21:11 the whole city aglow with the glory of God emits a jasper-like radiance. So the jasper wall speaks of the emission of the glory of God (Mounce).

Revelation 4:3 (KJV) And he that sat was to look upon like a jasper and a sardine stone: and there was a rainbow round about the throne, in sight like unto an emerald.

Revelation 21:11 (KJV)  Having the glory of God: and her light was like unto a stone most precious, even like a jasper stone, clear as crystal; 

The statement “the city was pure gold” means that the city shone like a mass of pure gold. This contrasts with the jasper luster of the city wall. The additional “like unto clear glass” pictures ideal gold so pure that it is transparent. This surpasses any gold known in this present creation. The same essential feature marks the city’s golden streets in v21, with the present verse an apparent reference to the city’s buildings, towers, or roofs seen from outside the city (Alford, Lee, Swete).

Revelation 21:21 (KJV)  And the twelve gates were twelve pearls; every several gate was of one pearl: and the street of the city was pure gold, as it were transparent glass. 

[Robert L. Thomas, Revelation 8-22 – An Exegetical Commentary, Moody 1995, 468-469]