Vintage Sterling Chrysoprase Screw back earring 1/2"LxW in nice condition. Chrysoprase, chrysophrase or chrysoprasus is a gemstone variety of chalcedony (a cryptocrystalline form of silica) that contains small quantities of nickel. Its color is normally apple-green, but varies to deep green. The darker varieties of chrysoprase are also referred to as prase.This would be a nice gift for holidays.