Alexandrite is gem-quality color-change chrysoberyl (BeAl₂O₄), the classical color-change benchmark, discovered in the Russian Ural Mountains in 1830. Different mineral species from Zultanite (color-change diaspore), different hardness (8.5 vs 6.5–7 Mohs), and different price band — alexandrite trades at USD 5,000–70,000+/ct, an order of magnitude above Zultanite. This hub indexes Zultpedia entries comparing alexandrite with Zultanite as a reference benchmark.