Red and black agate, onyx and sterling silver necklace

unusually dark red agate rectangle hangs from a strand of carved agate beads surrounded by large onyx and smaller black agate and sterling silver beads. graceful double link sterling chain lengthens the necklace. focal assembly is 1 7/8" long and 1 1/8" wide. bead strand is 19" long plus 5" extender chain.