坦桑石（Tanzanite），蓝或蓝紫色的多色性宝石，是黝帘石的变种，也是十二月的诞生石。

• 斜方晶系
• 比重：3.35
• 折射率：1.688 - 1.70
• 莫氏硬度：6 - 7

Tanzanite is the blue/violet variety of the mineral zoisite (a calcium aluminium hydroxyl Sorosilicate) belonging to the epidote group. It was discovered in the Mererani Hills of Manyara Region in Northern Tanzania in 1967, near the city of Arusha and Mount Kilimanjaro. Tanzanite is used as a relatively cheap gemstone, where it can substitute for the far more expensive sapphire after undergoing artificial heat treatment to form a deep blue coloration. Naturally formed tanzanite is extremely rare and is endemic only to the Mererani Hills.