Understanding the appeal of the sparkling rock, the Smithsonian is exhibiting seven of the world’s rarest diamonds at the Natural History Museum through September 15. On loan for exhibit are the DeBeers Millennium Star (by far the biggest of the bunch at 203.04 carats), the yellow Allnatt (101.29 carats), the Steinmetz Pink (59.60 carats), the Heart of Eternity (blue, 27.64 carats, pictured in the middle of this page), the Pumpkin Diamond (orange of course, 5.54 carats), the Ocean Dream (blue-green, 5.51 carats), and the Moussaieff Red (5.11 carats). The Smithsonian, of course, already has the infamous Hope Diamond on display. (Here’s a page of famous diamonds.)