All About Tanzanites
Tanzanite has become one of the symbols of Tanzania because it is completely unique to this incredible country. It is found only in Merelani, a five square mile area at the foothills of Mount Kilimanjaro. Although it is said to have formed over 585 million years ago during the geological events that resulted in the formation of the rift valley, it remained undiscovered until just over fifty years ago.
Tanzanite is also exceptional because it is a trichroic gemstone, which means it has three axis of color. The mineral name of Tanzanite is Zoisite and it is found naturally in a variety of colors ranging from blue and violet with flashes of red to different shades of green, yellow, brown and even pink. The multi-colored gemstone is then carefully heated at 500 degrees Celsius to bring out the lustrous blue-purple that Tanzanite is famous for. The heating process does not enhance the color or change the saturation of the stone, so the quality of the gem remains the same before and after heating.
Tanzanite has a refractive index of 1.69 and a value of 6.5 – 7 on the Mohs scale. It is not a particularly hard gemstone, similar to Emerald but less brittle, and for this reason it is advised to be worn with some care. Tanzanites are graded according to the four C’s – which are color, clarity, cut and carat weight – although the grading system is not as standardized as that of diamonds. The color grading starts at the top with ‘AAA’, which are the stones with the deepest and most vibrant color, and goes to ‘AA’, ‘A’, ‘B’ and ‘C’ as the gemstones become lighter and the color less intense.
Clarity is measure of how transparent the gemstone is, and most desirable are the eye clean stones which are categorized as ‘IF’ and ‘VVS’. Heavily included stones also have a distinct beauty and are often set in silver jewellery and used to make tanzanite beads.
The cut of a gemstone is chosen to carefully to best suit each piece while producing the least amount of wastage. There are many classic shapes including oval, pear or tear drop, round, trillion, cushion, heart and princess or emerald cut. Gem cutting is a very precise process in which each facet of the stone is carefully cut and polished by the qualifiedand experienced professionals in our lapidary to give the finished gemstone maximum sparkle, brilliance and symmetry.
The weight of cut gemstones is measured in carats and one carat is equal to one fifth of a gram. The size a stone appears to be depends on both the carat weight of the gem and the proportions of its cut. All of our Tanzanites are certified by an accredited laboratory.