What makes an even better December birthday gift than pretty heart-shaped earrings? Pretty heart-shaped earrings with the December birthstone! Made from sterling silver, these earrings in a pull through style display a heart-shaped tanzanite cubic zirconia crystal hanging from a 6cm chain and 1.7cm pin. Stamped with a 925 metal mark, the earrings weigh 0.8 grams as a pair. The crystal measures 6mm high, 5mm wide and 2mm deep.