Considering that tanzanite is found in only one place on earth and that this source is slowly diminishing, tanzanite is still relatively inexpensive compared to more freely available precious gemstones like diamond, sapphire, emerald and ruby. As it is unlikely that an alternative source of tanzanite will ever be found, tanzanite offers exceptional investment potential. slowly diminishing, tanzanite is still relatively inexpensive compared to more freely available precious gemstones like diamond, sapphire, emerald and ruby. As it is unlikely that an alternative source of tanzanite will ever be found, tanzanite offers exceptional investment potential.