Vintage Amethyst 9k Gold Brooch By HJ - 4.2 Grams . The quality of the amethyst gemstone is fantastic, the colour is just beautiful. The style and design is just wonderful. It weighs 4.2 grams. It is fully hallmarked with the Birmingham assay mark, crown, 375, the makers mark "HJ" and date letter "s" for 1992. It measures approx 4.7 cm across. Excellent condition.