This is the Shekinah, the visible manifestation of Gods presence. Because of His presence, the eternal city has no need for the light of the sun or moon (Isa. Isa. 66:19-20; Rev. Rev. 22:5+). See commentary on Revelation 22:5. See The Abiding Presence of God.
Her light was like a most precious stone
Her light will be like a city that is set on a hill which cannot be hidden (Mtt. Mat. 5:14).
like a jasper stone
Her walls are of jasper (Rev. Rev. 21:18+) and her first foundation is adorned with jasper (Rev. Rev. 21:19+).
clear as crystal
Because of how jasper (ἰάσπιδι [iaspidi] ) is described by Scripture, some think it is not the jasper we know, but perhaps diamond. See commentary on Revelation 4:3. The purity and clarity of the city is consistently emphasized (Rev. Rev. 21:18+, Rev. 21:21+; Rev. 22:1+). The description of her pure light recalls the sea of glass under the heavenly throne (Eze. Eze. 1:22; Rev. Rev. 4:6+; Rev. 15:2+). As we have seen, there is a close analogy between the Church and the New Jerusalem, both being the Lambs wife (Rev. Rev. 19:7+; Rev. 21:2+, Rev. 21:9+). The purity and preparation of the New Jerusalem are closely analogous to Christs purification and preparation of the Church:
Husbands, love your wives, just as Christ also loved the church and gave Himself for her, that He might sanctify and cleanse her with the washing of water by the word, that He might present her to Himself a glorious church, not having spot or wrinkle or any such thing, but that she should be holy and without blemish. (Eph. Eph. 5:25-27)