Altar stone
In Exodus 20:25, this signifies truths formed from good, or good in form, to signifies that nothing of self-intelligence should be involved in its forming. (Apocalypse Explained 391[21, 21])
Arcana Coelestia #577
577. Twelve means faith, or those things in their entirety that belong to love and faith deriving from it. Many details from the Word may confirm this - the twelve sons of Jacob and their names, the twelve tribes of Israel, and the Lord's twelve disciples. These matters however will in the Lord's Divine mercy be dealt with later on, in particular in Genesis 29, 30.