The tie tac does not have a gold mark but was tested with nitric acid and a "kee" tester to be 14k solid yellow gold. It weighs 1.3 grams and the natural boulder opal measures 1/2" x 7/16" which makes it approx 2.00 cts. The stopper on the pin is not gold and was not weighed with the piece. It is in excellent condition.