Strong's #3539: kadkod (pronounced kad-kobe')

from the same as 3537 in the sense of striking fire from a metal forged; a sparkling gem, probably the ruby:--agate.

Brown-Driver-Briggs Hebrew Lexicon:

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kadkôd

1) a precious stone (maybe ruby, agate)

Part of Speech: noun masculine

Relation: from the same as H3537 in the sense of striking fire from a metal forged

Usage:

This word is used 2 times:

 

Isaiah 54:12: "And I will make thy windows of agates, and thy gates of carbuncles, and all thy borders"
Ezekiel 27:16: "purple, and embroidered work, and fine linen, and coral, and agate."