Brass and Green Agate Gemstone Necklace.Metal is bronze plated alloy with genuine 14mm green agates gemstones. And a pretty Green Agate heart in the rear that can also be worn in the front. 17" long, 2 " brass chain, 19" total length Agate is a rock consisting primarily of cryptocrystalline silica, chiefly chalcedony, alternating with microgranular quartz. It is characterized by its fineness of k a of color. Agates come in a variety of forms and are named after the Achates river, now called