Exotic and velvet blue with a deep rich overtone of purple, tanzanite is certainly one of a kind. Rare, valuable and collectable, it is also found in only one place on the entire planet: the Merelani Hills of Tanzania, in the shadow of Mount Kilimanjaro.
Only discovered in 1967, tanzanite has become one of the world’s most popular gemstones. Tanzanite is available in a variety of shapes and sizes. Rarely pure blue, tanzanite almost always displays its signature overtones of purple. In smaller sizes, tanzanite tends toward lighter shades of lavender and periwinkle. In sizes above 10 carats, tanzanite can show deeper, richer intense blue colour.
Tanzanite is trichroic: that is, it shows different colours when viewed in different directions. One direction is blue, another purple, and another bronze, adding subtle depths to the colour. When tanzanite is found in the ground, the bronze colour dominates. However, with gentle heating, the cutter can watch the blue colour bloom and deepen in the stone.
Legend has it that the affect of heat was first discovered when some brown zoisite crystals laying on the ground with other rocks were caught in a fire set by lightning that swept through the grass covered Merelani hills northeast of Arusha. The Masai herders who drive cattle in the area noticed the beautiful blue colour and picked the crystals up, becoming the first tanzanite collectors.
Tanzanites with a colour that is more blue than purple tend to be more expensive because the crystals tend to form with the blue colour axis oriented along the width of the crystal instead of the length. That means that if the cutter chooses to maximize the purity of the blue colour, the stone cut from the rough will be smaller and will cost more per carat. The blue colour, however, is so beautiful that the sacrifice is often worth it.
Tanzanite jewellery is a little more delicate than other gemstone jewellery and should not be set in a ring that will be worn during strenuous activity. Never clean tanzanite in an ultrasonic cleaner or resize or repair a ring set with tanzanite without having the gem removed because the stone could shatter in the heat of a torch.
Tanzanite is available in a variety of shapes and sometimes in large sizes that are perfect for an important necklace. Clean with mild dish soap: use a toothbrush to scrub behind the stone where dust can collect.