Tanzanite Properties & Characteristics

This beautiful tanzanite ring demonstrates the unique properties and characteristics of this singular gemstone from Africa. Photo ©2020 EraGem Jewelry   Tanzanite belongs to the larger mineral family called zoisite. As such, it shares its basic structure with the other members of its family. However, the inclusion of vanadium in the crystal structure sets it apart from its brown, gray, and colorless cousins. Furthermore, this spectacular bluish-purple stone is found in only one place in the world - Tanzania, in Africa.  

The Mineral Tanzanite

As a member of the zoisite family, this gorgeous African gemstone features a base of calcium, aluminum, and silica. (source) Like other zoisite minerals, tanzanite grows into prismatic, and at times elongated crystals. (source) An infusion of vanadium in the crystal structure affords tanzanite its blue coloring. Color remains the primary factor for determining the gem's quality.  

Gemstone Quality Tanzanite

According to the GIA, the 4Cs apply to Tanzania's special gem: Clarity, Cut, Carat Weight, and Color. (source) The cleaner the stone, meaning the fewer inclusions within the crystal, the higher the clarity, and therefore the higher the quality. While oval and cushion cuts prove the most popular cuts for the transparent blue crystal, cutters can fashion it into a wide variety of shapes. As always, maximizing for color and carat weight remain important decisions for gem cutters working with this gemstone. With tanzanite, carat weight directly affects color. The more deeply saturated the color, the higher the value. With tanzanite, the stone tends to lose saturation as carat weight decreases. (source) Therefore, cutters must carefully consider how much carat weigh to sacrifice for the cut they desire. Not surprisingly, those with a deeper shade of blue prove more valuable than pale blue stones. In fact, the most desirable specimens possess a deep blue color with a hint of purple trimming the edges. (source)  

Pleochroism

In addition to its striking blue color, tanzanite features another distinctive color property - pleochroism. Defined as the ability to show different colors depending on which direction the crystal is viewed, pleochroism proves a useful characteristic for identifying this gorgeous African gem. (source) To witness this incredible phenomena, gently tip your stone back and forth. At one angle, it will appear deeper blue. From another, its purple hues pop. In some cases, you might even witness a hint of red-violet or yellow-green. (source) In the rough, tanzanite actually displays trichroism, meaning it exhibits three distinct colors - brown, blue, and purple. (source) To enhance the blue tones, view your gem under incandescent light. Meanwhile, to see more purple hues, view it under the natural light from the sun. ~Angela Magnotti Andrews