In Revelation 21:18 John had described the “pure gold” of the city as “like clear glass.” This time, however, John uses a different adjective, that is, “transparent.” The emphasis, then, is placed on the degree of purity, that is, so pure that you can see through it.
21 And the twelve gates were twelve pearls, each of the gates made of a single pearl, and the street of the city was pure gold, like transparent glass.