In Ezekiel 27:16, coral signifies knowledge of good. (Arcana Coelestia 1232)

Works, emeralds, purple broidered work, fine linen, coral, and agate, (Ezekiel 27:16), signify knowledges of good.

3645. The whole of the Lord's kingdom is a kingdom of ends and purposes, so that not even the least thing occurs there which does not have a purpose to achieve some end in view. I have been allowed to perceive clearly this Divine sphere of ends and purposes, some of which are beyond description. Every single thing flows from that sphere, and is governed by means of it. Insofar as his affections, thoughts, and actions have within them the end in view of doing good from the heart, man, spirit, or angel dwells in the Grand Man, that is, in heaven. But insofar as man's or spirit's end in view is to do evil from the heart, he dwells outside the Grand Man, that is, in hell.