The twelve precious stones in the foundation of the New Jerusalem signify every aspect of the doctrines of the New Jerusalem, in their order, from the literal sense of the Word -- as understood by people who directly approach the Lord and live according to the commandments of the Ten Commandments by shunning evil as sins.

These twelve precious stones signify the same thing as the twelve tribes of Israel, that is, all the goods and truths of the church and its doctrine in their order.

Similarly, the twelve apostles signify every aspect of doctrine concerning the Lord, and life conforming to His commandments. This is why the names of the twelve apostles of the Lamb were written in these twelve foundations.

In the same vein, the stones in the breast-plate of Aaron were inscribed with the names of the twelve tribes of Israel.

(Reference: Apocalypse Revealed 915; Revelation 21:19-20)