It costs from about 2.5 to 20 thousand dollars per gram, or from 500 to 4 thousand per carat. Taaffeite is a jewel of purple color said to be a million times rarer than diamonds. Because of its extreme rarity it is used only as a gemstone. Taaffeite is a very rare mineral , a complex of oxide (hydroxide), magnesium, beryllium and aluminum, which is close to the spinel and difficult distinguishable from it. It occurs as isolated euhedral crystals. Of spinel crystals of which it is most often found, and other similar minerals visually distinguish the effect of the presence of birefringence, stones which can be found under further investigation by modern methods. Several hundred copies of taaffeita (the largest of the known taafeite weighs 9.31 carats) and was found in Tanzania only in recent years. This is a rare and very valuable gem. Processed cut. The world price of faceted taafeite ranges from 2,000 to $ 10,000 per carat .