From BiblePortal Wikipedia

Hastings' Dictionary of the New Testament [1]

(χρυσόπρασος, from χρυσός, ‘gold,’ and πράσον, ‘a leek’)

This stone is the tenth foundation of the wall of the New Jerusalem ( Revelation 21:20). The name is now applied to an apple-green variety of chalcedony or hornstone, prized in jewellery and sometimes used for mural decorations. But this chalcedony was probably unknown to the ancients, and the χρυσόπρασος of the Greeks was ‘not improbably our chrysoberyl’ ( Encyclopaedia Britannica 11 vi. 321). The word is not found in either of the Septuagintlists of precious stones ( Exodus 28:17-20,  Ezekiel 28:13) with which the writer of Rev. was familiar.

James Strahan.

Smith's Bible Dictionary [2]

Chrysoprase. Chrysoprase occurs only in  Revelation 21:20. The true chrysoprase is sometimes found in antique Egyptian jewelry set, alternately, with bits of lapis-lazuli. It is a problem, therefore, that this is the stone named as the tenth in the walls of the heavenly Jerusalem.

King James Dictionary [3]

CHRYSOPRASE, n. A mineral, a subspecies of quartz. Its color is commonly apple green, and often extremely beautiful. It is translucent, or sometimes semi-transparent its fracture even and dull, sometimes a little splintery, sometimes smooth and slightly conchoidal its harness a little inferior to that of flint.

Webster's Dictionary [4]

(n.) An apple-green variety of chalcedony, colored by nickel. It has a dull flinty luster, and is sometimes used in jewelry.

Holman Bible Dictionary [5]

 Revelation 21:20