Emerald, the May birthstone, is a green variety of beryl colored by chromium and sometimes vanadium. Associated with Taurus and Gemini, emerald is the Heart Chakra stone, promoting growth, renewal, and heart-centered wisdom. In Vedic astrology, emerald (Panna) is the gemstone of Mercury. Cleopatra was famously obsessed with emeralds, and the finest specimens rival diamonds in value.