Arcana Coelestia #9508
9508. 'And a cubit and a half its breadth' means what is complete so far as truth is concerned, also as above, in 9488.
Chalcedony
In Revelation 21:19, this signifies truth that is visible in the spiritual sense of the Word. This is the third stone in the foundations of the New Jerusalem. (Apocalypse Revealed 915)