At the American Museum of Natural History, one of the city’s great treasures—the Allison and Roberto Mignon Halls of Gems and Minerals—has been redesigned and refreshed. The new theme is evolution; specifically, how minerals have evolved over vast stretches of time. And the new halls are airier, brighter, more modern, even as the mysterious vibrancy of colored stones and minerals may remind you of that old Jules Verne movie Journey to the Center of the Earth. The exhibition includes giant garnets over a billion years old, and 2000 gems, carvings, and jeweled pieces. As of November 9, 2021, the Okavango Blue Diamond, from the Republic of Botswana, is part of a presentation on ethically sourced diamonds. This brilliant gem is the size of a quail’s egg and the color of the heavens. —L.J.