Numerous sellers of tanzanite use the fact that tanzanite is only found in one small area to promote the material’s rarity. A counter to that is that the world is an enormous planet and zoisite is not an extremely rare mineral.

How many people and companies are out looking for samples of zoisite and taking them back to a lab to see if they will heat to a blue color? Probably very few. However, if the price skyrockets and a lot of exploration occurs, that work might discover so much “tanzanite-quality” zoisite that the price falls to historically low levels. Oil, natural gas and other commodities are not at historic high prices today because technology and exploration has identified enormous new deposits.

Some sellers also suggest that the value of tanzanite will skyrocket when the known deposits are mined out. That might occur initially. No one knows for sure. A counter is that the price might initially rise but then, when no new tanzanite is entering the market, the price will decline to low levels as the gem loses its visibility and popularity and fades in the minds of buyers.

What happens when tanzanite supplies deplete cannot be predicted. People who invest in tanzanite might make money, but profits are not guaranteed.

Disclosure: Tanzanite is one of the author’s favorite gems. He owns a few faceted stones and a few pieces of rough for gemological study. He has no intentions of buying tanzanite as an investment. He would not be surprised if tanzanite was found in other parts of the world.