John the Apostle
Revelation 21:20ESV·traditional attribution

the fifth onyx, the sixth carnelian, the seventh chrysolite, the eighth beryl, the ninth topaz, the tenth chrysoprase, the eleventh jacinth, the twelfth amethyst.

Matthew Henry Presbyterian @wholebiblehenry

We have already considered the introduction to the vision of the new Jerusalem in a more general idea of the heavenly state; we now come to the vision itself, where observe, I. The person that opened the vision to the apostle - one of the seven angels, that had the seven vials full of the seven last plagues, Rev 21:9.

Commenting on Revelation 21:9-27

John Gill Reformed Baptist @doctorgill

And the twelve gates were twelve pearls,.... Denoting the purity and preciousness of Christ, by whom the saints enter, and of the saints who enter in thereat, as well as of the place into which they enter. Every several gate was of one pearl; the pearl of great price, the Lord Jesus Christ, who is the only gate, door, and way into this happy state...

Albert Barnes Presbyterian @notesbybarnes

Verse 20. The fifth, sardonyx. This word does not occur elsewhere in the New Testament. The name is derived from Sardis, a city in Asia Minor, (Barnes on "Re 3:1",) and ονυξ--a nail--so named, according to Pliny, from the resemblance of its colour to the flesh and the nail. It is a silicious stone or gem, nearly allied to the onyx. The colour is a reddish yellow, nearly orange.--Webster's Dic.