She'll be a lucky lady to receive these earrings with a heart-shaped crystal, and even more so if her birthday is in November, as the genuine sky blue topaz crystal is the November birthstone. The topaz crystal measures 5mm x 5mm. Made from 9ct yellow gold with a 375 metal mark, the stud earrings have a pin width of 0.65mm and front to back distance of 12.5mm. They weigh half a gram.