“And the (material) on which the (wall was) built (around) her (was) iaspis, (and) the city (itself was all) pure gold likened to pure glass.” (v. 18)
The expression h( e)ndw/mhsi$ tou= tei/xou$ is a bit awkward to translate literally into English. It properly would refer to the inner structure on which the wall was built—this is the fundamental meaning of the noun e)ndo/mhsi$ (“building on/in”). Thus the wall at its core was made of precious stone; however, it is perhaps more likely that the full expression is simply intended as a public announcement of how the wall was constructed, i.e. it was made (entirely) of precious stone. The particular stone is i&aspi$ (iaspis, “jasper”), as in the general description of the city’s splendor in verse 11 (cf. the earlier note, and compare its use in 4:3). It is indicative of the divine/heavenly character of the city, extending all the way to its outer walls.
The city itself was golden, or made of “gold”, signifying primarily its purity (kaqaro/$, “clean[ness]”), as would reflect the holiness of God (and His people), but also characteristic of the divine brightness and splendor (or ‘glory’, do/ca, v. 11). Gold is a natural symbol for the splendor of a city or of an ideal/heavenly location. In Tobit 13:16, in the glorious Jerusalem of the future, the towers and fortifications of the city are built with gold. The clarity of the city (“like pure glass”) is another traditional image to express its divine/heavenly character.
“The (foundation)s set down of the (wall) built (round) the city, having been adorned with all (kinds of) valuable stone (are as follows):
the first (stone) set down (was) iaspis, the second saphiros, the third (the) copper-like (stone) [chalkedon], the fourth smaragdos, the fifth sardonyx, the sixth sardios, the seventh (the) golden-stone [chrysolithos], the eighth beryllos, the ninth topazos, the tenth gold-prason, the eleventh hyakinthos, the twelfth amethystos” (vv. 19-20)
There were twelve large foundation-stones upon which the walls were built, three on each side, corresponding to the twelve apostles (v. 14, see the prior note). Each of these great stones was itself covered (“adorned”, vb kosme/w) with valuable stone of different colors. The imagery is derived primarily from Isaiah 54:11-12, where it applies figuratively to the promise of a future restoration of Israel:
“…see! I will cause your stones to be laid down with (richly-colored) powder, and your foundations with cutting-gems [sappîrîm]; I will set your sun-(marker)s (with) sparkling (stone), and your openings [i.e. gate-ways] with fiery stones, and all your borders with stones of delight!”
The meaning and derivation of the technical terms for precious stones, etc, are as uncertain in the Isaian prophecy as they are in Greek of Revelation. The emphasis in Isa 54:11 however is clearly two-fold: (1) stones decorated with rich color, and (2) the foundation-stones made of precious gems (Hebrew ryP!s^ = Greek sa/pfiro$, ‘sapphire’). The Greek terms primarily relate to different colors and hues, as is indicated by words like “copper-like” (xalkhdw/n) and “golden-stone” (xruso/liqo$); however, the precise meaning remains uncertain, and they are typically transliterated in English, as I have generally done above. The first two are most prominent, and essentially represent all the rest: i&aspi$ (“jasper”) and sa/pfiro$ (“sapphire”). The first is probably meant to indicate a stone of bluish or blue-green color, while the second is bright/light blue, perhaps to be identified as lapis lazuli. They feature in ancient descriptions of theophanic visions, such as in Exodus 24:10 and Ezekiel 1:22ff, 26ff (LXX).
The twelve stones in vv. 19-20 correspond generally with those in two important Scriptural lists (in the Greek LXX)—(1) the stones set in the ‘breastpiece’ (/v#j)) of the Israelite High Priest (Exod 28:17-20; 39:10-13), and (2) the gems present in the Garden of God, mentioned in Ezekiel’s oracle against Tyre (Ezek 28:13). The stones in the High Priest’s breastplate are more immediately relevant, in that they number twelve and correspond to the twelve tribes of Israel (Rev 21:12ff). They are also laid out in four rows, similar to the four sides of the heavenly city. However, the reference to the Garden of God in Ezekiel 28:13, reflects the heavenly paradise of the “new Jerusalem” (note the allusions to Eden and the Creation account in chap. 22, to be discussed). The idea of jewels/gems growing in the divine/heavenly “garden” is a traditional mythological motif, going back to at least the time of the Gilgamesh Epic in the mid-2nd millennium B.C. (Tablet 9, lines 170-190).
A much later example, closer in time to the book of Revelation, is found in Lucian’s (satirical) True History (11-13), providing a description of a utopian city in the ‘isle of the Blessed’ that is roughly similar to that of the “new Jerusalem”:
“The city itself is all of gold and the wall around it of emerald. It has seven gates, all of planks of cinnamon. The foundations of the city and the ground within its walls are of ivory. There are temples…built of beryl, and in them…altars of amethyst…” (citation and translation from Koester, p. 830)
The description here in Revelation concludes with verse 21:
“…and the twelve gate-ways (are) twelve pearls [margari=tai]—each one of the gate-ways was (made) out of one pearl. And the broad [i.e. main] (street) of the city was pure gold, as of shining through [i.e. clear/transparent] glass.”
In some ways, pearls are even more valuable than gold (e.g., the illustration in Matt 13:45-46), and it would require an immense pearl to construct a massive city gate-way out of one. As noted in verse 18, the city itself was made out of “pure gold” (xrusi/o$ kaqaro/$), and this includes even the wide main street (platei=a) of the city. Paved streets were relatively rare in the ancient world, but the main streets of a number of important Roman cities were given costly pavement, which could be dedicated to particular deities (or to the emperor; Koester, p. 820). Here the main street of the “new Jerusalem” is paved with translucent gold, in honor, we might say, of its dedication to God. In the description of the glorious future Jerusalem in Tobit 13:16, the streets are similarly paved with rubies and precious gems.
There may be an intentional contrast with the ‘main street’ of the earthly Jerusalem, symbolic of the wicked “great city”, in 11:8, where God’s faithful witnesses are slain. As previously noted, the heavenly city of the “new Jerusalem” (the Bride) is set in direct contrast to the wicked “great city” of earth (Babylon, the Prostitute). In 17:4, “Babylon” is similarly adorned with gold and jewels; now it is “Jerusalem” (the Bride) who bears this precious decoration, only in holiness and purity instead of wickedness.
References marked “Koester” above, and throughout this series, are to Craig R. Koester, Revelation, Anchor Bible [AB] Vol. 38A (Yale: 2014).