Tanzanite is a rare precious gemstone and the blue to violet variety of the mineral zoisite, famous for its striking trichroism—displaying blue, violet, and burgundy hues depending on the viewing angle. Discovered in 1967 near Mount Kilimanjaro in Tanzania (the only known commercial source), it has a hardness of 6.5–7 on the Mohs scale, making it suitable for jewelry but requiring care. Prized for its vivid color and extreme rarity, tanzanite is the birthstone for December and has quickly become one of the most sought-after modern gemstones.