Concise Bible Dictionary:

1. zekukith (Job 28:1717The gold and the crystal cannot equal it: and the exchange of it shall not be for jewels of fine gold. (Job 28:17)), probably glass highly ornamented, such as was made in Egypt: it is here classed with gold; but wisdom, the gift of God, far exceeds such things in value.
3. κρύσταλλος. John saw a sea of glass like unto crystal (Rev. 4:66And before the throne there was a sea of glass like unto crystal: and in the midst of the throne, and round about the throne, were four beasts full of eyes before and behind. (Revelation 4:6)); the water of life and the jasper stone were seen “clear as crystal” (Rev. 22:11And he showed me a pure river of water of life, clear as crystal, proceeding out of the throne of God and of the Lamb. (Revelation 22:1)). The ancient glass may have been “clear” in the sense of not having spots and blemishes, without its being wholly transparent.