Sophia Hirsh, managing director of the jewelers Hirsh London, also likes colored gems, but in offbeat shapes — like a 10.8-carat black opal heart pendant with a shape that she described as ...

Even then, the heart in question wasn’t quite the shape that’s recognizable today. Francesco Barberino's Documenti d'amore, circa 1320 The Shape of the Heart by Pierre Vinken. Elsevier, 2000.