The foundations are adorned with precious stones (Rev. Rev. 21:19+). See commentary on Revelation 21:19.
By faith Abraham obeyed when he was called to go out to the place which he would receive as an inheritance. And he went out, not knowing where he was going. By faith he dwelt in the land of promise as in a foreign country, dwelling in tents with Isaac and Jacob, the heirs with him of the same promise; for he waited for the city which has foundations, whose builder and maker is God. (Heb. Heb. 11:8-10)See Twelve: Jewish Tribes, Completeness.
on them were the names of the twelve apostles of the Lamb
The MT and NU texts have the twelve names of the twelve apostles. Regarding the distinction between the names of the tribes of Israel and the apostles of the Lamb, see commentary on Revelation 21:12. The question arises as to which twelve names are represented? Eleven of the twelve seem clear enough, but who will be listed as the twelfth? Will it be Judas , the original apostle chosen by Jesus (John John 6:70)? Or perhaps Matthias , chosen by the eleven to replace Judas (Acts Acts 1:26)? The third possibility is Paul , chosen by the Lord (Acts Acts 9:3-6, Acts 9:15-16). While it is impossible to know, and perhaps not of great importance, we are inclined to think the twelfth name will be that of the Apostle Paul, for it seems impossible that his name would not appear on a foundation as a major contributor to the early church and the New Testament. On the other hand, like the scars which remain on Jesus glorified body (John John 20:27 cf. Rev. Rev. 5:6+), perhaps the name of Judas will be retained as a memorial of Christs atoning work on the cross. The apostles, along with the prophets, are considered the foundation of the spiritual temple in the Lord (Eph. Eph. 2:19-22 cf. Eph. Eph. 3:5; Eph. 4:11). Concerning Jesus title as Lamb, see commentary on Revelation 5:6.