From BiblePortal Wikipedia

Webster's Dictionary [1]

(1): ( a.) Having a fine light blue color, like that of choice mineral turquoise.

(2): ( n.) Alt. of Turquois

Holman Bible Dictionary [2]

Minerals And MetalsAntimony

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [3]

a Persian gem of a peculiar bluish green color, which was very generally used in the Middle Ages for the adornment of every species of sacred vessel, e.g. the chalice, ciborium, altar-cross, miter, and pastoral staff.