AGATE, a precious stone (Isa 54:12) which is a variegated chalcedony (q.v.) and similar to jasper (q.v.) (cf. NEB Ezek 27:16), being very fine grained silica (silicon dioxide). It is distinctive in consisting of alternating layers of various colors, mainly white, bluish and pale brown. Most agates occur in cavities in ancient lavas such as those near Lake Tiberias and northeastward into Syria. The successive layers are approximately parallel to the sides of the cavity resulting from reaction to silica gel, which coagulated from water carrying silica in solution, with the adjacent iron-bearing rock.