Boyd’s Bible Dictionary:
(from Chalcedon). A many-colored precious stone of the agate variety (Rev. 21:19).
Concise Bible Dictionary:
Blue Chalcedony
A precious stone, mentioned but once: it forms one of the foundations of the wall of the heavenly Jerusalem: it cannot be identified with any certainty (Rev. 21:19).
Strong’s Dictionary of Greek Words:
Transliteration:
chalkedon
Meaning:
from 5475 and perhaps 1491; copper-like, i.e. "chalcedony"
Jackson’s Dictionary of Scripture Proper Names:
copper-like: flower-like