What are the pearls in Revelation 21:21 a type of?

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. (Rev 21:21)

Jesus described the gospel as a “pearl of great price” (Matt 13:46). If this is the allusion then it means that the entrance to the New Jerusalem is through the gospel.