Tanzanite is a blue to violet gemstone which is a member of the zoisite mineral and is pleochroic, which means that it shows different colours depending on the viewing angle.
In order to get the preferred blue or violet-blue hue, gem cutters must properly orient tanzanite gemstones. The vivid blue of tanzanite can rival fine sapphire and makes tanzanite an extremely desirable gemstone.
Tanzanite ranges in colour from ultramarine to sapphire blue. Under artificial light, it may appear more violet. Tanzanite's pleochroism means that it can appear blue or violet when viewed from different angles. Tanzanite has a higher colour saturation in gemstones of over 5 carats. The most desirable colour for tanzanite gemstones is a deep saturated blue or violet-blue.
Tanzanite is mostly faceted in both traditional and fancy shapes and a variety of cutting styles. When cutting tanzanite, lapidarists generally take cost into consideration, which means that tanzanite is often cut into ovals and cushions