Mineral zoisite, more widely known as Tanzanite, the purple-blue gemstone discovered in 1967 by a Masai tribesman, catapulted and marketed to the world the following year by Tiffany & Co. To achieve the exquisite internationally recognised hue, some crystals that begin as a green-grey, adopt the blue intensity after being heat treated. This is for the purpose of colour only, rather than an attempt to change the internal composition to ‘change’ the gem. Tanzanite has strong pleochroism allowing for an array of colour display whether beneath the African sun at the Merelani Mine, or presenting a suite to discerning customers in your retail boutique on Rodeo Drive. There is a direct correlation between gem source and value, and with the ever-increasing difficulty of tracing gem sources, the determined (and courageous) individual heads to the mine for added certainty and to negotiate a bargain!… The advantage and simultaneously the disadvantage is the single-source for Tanzanite; available only at the foothills of Mount Kilimanjaro, further adding to the appeal of the gem, proverbial reverence, and constantly shifting price. We are almost at the fifty year anniversary of discovery, yet experts project no more than a few decades remain for us to unearth larger quantities/any gems at all. It is inevitable that abundant sources seldom last long, often leaving reverberations in the industry. It is also worth noting known sources have in the past been declared depleted, and unexpected discoveries occur. Thankfully we have the opportunity to admire jewel-art by jewellers such as Mark Schneider, whose Work can be seen on display at The Smithsonian Institution in Washington D.C.