1.80 cttw Tanzanite Stud Earrings 14K Yellow Gold (6 MM Round Cut) 30 Day Easy Returns. Jewelry Gift Box Included 14K Yellow Gold Natural Tanzanites are heat treated to produce a range of hues between bluish-violet to violetish-blue. This is done through mild heating in the production process. Due to the permanent nature of this treatment the gemstones do not alter in quality, only in appearance. The total carat weight of the 2 stones is 1.80 CT