Tanzanite Necklaces - The Gemstone For The 24th Wedding Anniversaries Tanzanite is a rare and highly valued gemstone recognized for its brilliant blue-violet hue. It is a stunning purple stone. It is a variety of the mineral zoisite, a member of the epidote mineral family. Pleochroism, or the ability to change color when viewed from different angles, is a characteristic of tanzanite. Depending on the crystal orientation, they reflect blue, violet, or burgundy hues. This captivating gemstone's clarity can range from transparent to translucent, and it typically has internal insertions known as silk.