TANZANITE
Tanzanite is a unique and precious gemstone, considered to be 1000 times rarer than diamond. It is a variety of the mineral zoisite and is found in only one locality world-wide - at the foothills of Mount Kilimanjaro in northern Tanzania, East Africa. Although tanzanite's unique colour, poised intriguingly between blue and violet, makes it highly desirable, it is a relatively soft and fragile gemstone. Rated with a hardness of 6.5 - 7 on Moh's hardness scale (for comparison, diamond, the hardest mineral, is rated 10), tanzanite should be carefully looked after. Even though tanzanite is better suited to earrings and pendants as a result of its softness, a suitable setting in a dress ring and careful maintenance will give years of pleasure to a discerning owner.
Cut refers to the shape, facets and proportions of a tanzanite. The quality of the proportions of a cut tanzanite will significantly affect the resultant brilliance of the stone. A 'fine' cut ensures that the stone's facets reflect light to create maximum brilliance. Tanzanites are cut into a variety of shapes, predominantly determined by the shape and size of the rough crystal form.
Colour refers to the blue in tanzanite and its degree of violet saturation. The predominance of either blue or violet in a stone is indicated by "B" or "V" respectively. The depth of colour, or saturation, of tanzanite is varied and ranges from exceptional to pale. The deeper the colour of tanzanite, the more valuable it is.
The clarity of a tanzanite refers to the degree of natural flaws and inclusions within a polished stone. Polished tanzanite stones are graded under 10x magnification through a jeweller's loupe and may range in clarity from Eye Clean to Heavily Included. Stones that are classified as Eye Clean or Slightly Included contain inclusions that are not visible to the naked eye and as such do not detract in any way from the beauty of the stone. Larger inclusions lead to classification as either Moderately or Heavily Included and these may be seen by the naked eye. The more flawless (less inclusions) a tanzanite contains, the more valuable it is.
Carat is the term used to measure the weight of a tanzanite stone. One carat is equivalent to 100 points (i.e. 0.25c equals 25 points) and a carat is 0.2g.
Information and images courtesy of the Tanzanite Foundation www.tanzanitefoundation.org
