Certificate number 1820006886 18 karat yellow gold bracelet set with twenty six (26) oval mixed cut natural Tanzanites stamped 585" "Identification: Natural Zoisite, Tanzanite Estimated carat weight: 4.16 ct. Shape and cutting style: Round Mixed Cut Color: Violetish Blue (Transparent) Measurements: 3.15 - 3.20 Tanzanite is commonly heated at low temperatures to improve its color. There is currently no testing method available to disclose such treatment.