Tanzanite is a blue gem that is produced commercially in one area of Tanzania, the Merelani Hills near the base of Mount Kilamanjaro and the city of Arusha. Tanzanite is a trade name for gem-quality specimens of the mineral zoisite, characterized by its blue color. It is known for its vitreous luster and pleochroic qualities – it appears to be different shades when it is viewed from different directions. While most of the world’s gems have been enjoyed for thousands of years, tanzanite was discovered for marketing in the late 1960s. It is now compared to sapphire in terms of blue gem stone popularity.