Natural Green Chrysoprase Smooth Polished Fancy Necklace Length is 18 Inches & Sizes 11mm to 25mm approx.Chrysoprase, chrysophrase or chrysoprasus is a gemstone variety of chalcedony (a cryptocrystalline form of silica) that contains small quantities of nickel. Called the stone of Venus, chrysoprase is the rarest and most valuable rich apple -green gemstone in the chalcedony family