In Revelation Chapter 21 God tells about the New Jerusalem. John was taken away to heaven, and was carried away in the Spirit to a mountain great and high, and he was showed the Holy City, Jerusalem, coming down out of heaven from God. It shone with the glory of God, and it's brilliance was like that of a very precious jewel, like a jasper, clear as crystal. It had a great, high wall with twelve gates, and with twelve angels at the gates. On the gates were written the names of the twelve tribes of Israel. There were three gates on the east, three on the north, three on the south and three on th west. The wall of the city had twelve foundations, and on them were the names of the twelve apostles of the Lamb. The foundation of the city walls were decorated with every kind of precious stone. (12 stones)
Foundation Gems of the New Jerusalem are identified with the Apostles, and they, in turn, with the twelve tribes over which they will rule; but the various colors of the gems suggest the sevenfold colors of the rainbow, the token of the covenant (Gen. 9:15). The combination of those colours produce the white light of the sun (for which see Matt. 13:43) figurative of the Sun of Righteousness and his healing beams (Mal. 4:1-2). As the Rainbow is the reflected multicolored glory of the Sun, so the gems represent the various aspects of God Manifestation, to be seen in its fullness in the age to come. The twelve gems of the Apocalypse should be considered with the twelve gems of the Breastplate, and the tribes represented thereby.
The King James Bible lists the stones as:
Chalcedony (It is called by the subvaritey name Known as Agate)
Sardius (NIV says Carnelian)