Let’s see what colors tanzanites are. Tanzanite is a transparent gem variety of the zoisite mineral. Its color is due to impurities of various chemical elements. For example iron and chromium contribute to green color, manganese – pinkish, vanadium – blue. The classic color of tanzanite is violet-blue, with variations in the direction of violet or blue, from light blue and lavender shades to dark blue and dark violet. Rare colors of gem zoisite are pink, green, yellow, lavender. The most valuable is considered vivid blue, sapphire color of tanzanite, with a small content of violet (vivid violetish blue).
For a long time tanzanite was considered by buyers and jewelers as a rare natural analog of natural sapphire, so the range of colors close to commercial sapphire varieties is still in demand. For example, Cornflower Blue and Vivid Blue (Royal Blue). But in all blue tanzanites, violet tint is also present. Also it is worth mentioning the most beautiful amazing polychrome specimens. They are also sometimes called multicolour tanzanites. In one such sample 2-3 shades are immediately presented. For example blue, green and purple. This distribution of shades is caused by two reasons that may be present simultaneously: zoning of the crystal, very strong pleochroism and also their combination.
Pleochroism is the property of a crystal to show different shades in different directions. It is present to one degree or another in many minerals, but in tanzanites it manifests itself very strongly. The main advantage is that each such specimen is essentially unique and individual, since there are no two equally same colored stones. If a crystal will go to the hands of a high-level cutter polychrome tanzanite unbelievably reveals its beauty, sometimes giving birth to amazing colors.
Such multicolour stones are extremely rare. It makes tanzanites truly nontrivial. But it happens that in some multicolor tanzanites the general perception of color becomes inexpressive since the shades overlapping each other and being reflected in the facets of the stone mix.