Tanzanite, named after Tanzania where it was discovered in 1967, resembles sapphire with a bluish violet colour but costs far less. Tanzanite gained popularity in the 80s and 90s and, despite its relative fragility, remains a popular choice for jewellery. Tanzanite comes out of the ground in only Tanzania and Kenya, making it relatively rare among gemstones. Determining the value of tanzanite, as with other gemstones, depends on its size, quality and colour and can only be authoritatively confirmed by a licensed appraiser.
Weigh the tanzanite on a jeweller's scale to determine its carat weight. If you don't have access to a jeweller's scale, estimate the weight on a scale that measures in fractions of a gram. Convert grams to carats by multiplying the number of grams by five.
Determine a starting value of the tanzanite by multiplying its carat weight by £292. Although diamonds and other gemstones increase in value per carat and larger sizes, tanzanite normally comes out of the ground in fairly large pieces, making its increased value less dependent on its large size than with other gemstones.
Examine the tanzanite under the jeweller's loupe. Subtract value per carat for every visible flaw that you see either in the stone itself or in its cut. Most tanzanite has very few, if any, flaws, so a flawed stone rapidly decreases in value. Although only a trained jewellery appraiser in your area can precisely determine how much a flaw decreases a stone's value, the at-home buyer can count on paying less than £260 per carat for stones with flaws.
Compare the colour of the tanzanite to the colour of deep rich sapphires. The more blue the tanzanite is, the more valuable it is. Tanzanites without any trace of violet in their colour can increase in value up to £325 per carat or more. Light blue or lavender tanzanites lose a bit of value and can sell for £260 per carat or less.
Compare the prices of tanzanites both locally and on the Internet to find the best value. Compare stones from reputable retailers and ask to see each under a loupe or magnified to judge its quality and cut.
Do not use heat such as a hairdryer or iron when wearing your tanzanite. Do not clean tanzanites in an ultrasonic jewellery cleaner. Because of tanzanite's fragility, treat it with care.