Tanzanite is often described as having shades of blue, violet, and purple. But is tanzanite actually blue or purple? The answer lies in the unique way this stone reflects and absorbs light.
Tanzanite belongs to the mineral family of zoisite and exhibits a phenomenon known as pleochroism. This means that tanzanite shows different colors when viewed from different angles. From one direction, tanzanite can appear blue and from another direction, more purple.
The reason for this is that tanzanite has two strong trichroic colors – blue and violet. Trichroism refers to how a gemstone displays different colors when viewed from different angles. In the case of tanzanite, the gem reflects blue and violet light strongly, which interact to make the stunning range of blue and purple shades.
Specifically, tanzanite absorbs yellow and green light while allowing blue and violet light to pass through. When looking down the pavilion (base) of the stone, the blue light is most apparent. But when looking through the crown (top), the violet hues stand out more. As light passes through the tanzanite crystal lattice, this color dichotomy emerges.
Tanzanite also often has a strong pleochroic effect ranging from a rich sapphire blue to a warm violet. So a single stone can showcase both cool blue and regal purple tones depending on the crystal orientation and planes of absorption. This makes each tanzanite stone unique in its exact mix of blue and violet shades.
The most prized tanzanite gems exhibit a strong violet-blue dichotomy. Stones of lower quality may appear muddy with weaker color zoning. Heat treatment is commonly used to intensify the colors and clarify the zoned pleochroism that makes tanzanite so fascinating.
So in summary, tanzanite is both blue and purple due to its inherent trichroic properties. It reflects blue light most intensely along one crystal orientation while reflecting more violet along another axis. Both blue and purple hues can be present in a single gem depending on lighting conditions and viewing angle. The interplay between violet and blue is what makes tanzanite so remarkable and is why it can rightfully be described as both a blue and purple gemstone.
The next time you examine a tanzanite under different light sources, watch how the balance of blue and purple shifts and changes. That color dance is the signature of this one-of-a-kind gem found only in the foothills of Kilimanjaro. Tanzanite captures both the cool tones of blue and the regality of purple in one exquisite stone.
