It is rare to find a collector with a deep understanding of both gemstones and design. This December, Sotheby’s Magnificent Jewels auction presents 35 pieces from one of the most thoughtfully assembled collections offered in recent years. Acquired through a path of passionate self-education and remarkable market foresight, this American collector developed a unique ability to analyze jewels on a microscopic level, burnished by a love of color and beauty. Click ahead to discover must-see jewels from her collection, ranging from whimsical designs by Jean Schlumberger and Cartier to the “big three” gemstones: a pigeon’s blood ruby, a “royal blue” sapphire and a no-oil emerald.