• Tanzanite was only discovered in 1967 by Ndugu Ngoma whose
discovery was finally recognised and acknowledged by the
Tanzanian Government in 1984.
• Tanzanite was originally called Zoisite and was renamed by Henry
Platt, Tiffany's Chairman in New York. The name only refers to
the blue gemstone and not to other colours of zoisite.
• Tanzanite is only found in a small area in the Merlani Hills near
Mount Kilamanjaro in Tanzania. The total mining area in which
Tanzanite is found is a mere 16 km² and remains the only known
source in the world. It is truly an "African" stone.
• The crystalline chemistry, optical properties and unique colour
coupled with it's relative rarity makes Tanzanite a very marketable
commodity in the global luxury goods market.
• Tanzanite is at least one thousand times more rare than diamonds.
It's rarity is due to the fact there is only one known source of
supply and that is a limited resource.
• The geological distribution of Tanzanite mineralisation is difficult
to estimate given the complex geology. This combined with
considerable variability in yields, i.e. carats per ton of rock mined,
produces a wide range of resource estimations. At present,
tanzanite reserves are estimated to lie in a range of 20 - 45 years, a
limited life in gemological terms.
• Quality for quality, Tanzanite is roughly one third the price of
• In 2003, The American Gem Trade Association named Tanzanite
as a December birthstone, adding to a list previously unchanged
• For most of the last 10 years, Tanzanite has ranked amongst the
top four selling gemstones in the U.S.A. by value.
• The market for Tanzanite is still relatively fragmented,
underdeveloped and imperfect, in sharp contrast to the diamond
market. The pricing structure is also imperfect and clear price
trends are difficult to quantify precisely. However, market
participants would guess that Tanzanite mid-market prices have
been rising some 15-20% per annum over the past 5 years.
• Tanzanite was formed approximately 585 million years ago by
high temperature and pressures associated with the techno-
magmatic formation of the African Rift Valley.
• Tanzanite is classified as a silicate, sub-class soro silicate and a
member of the epidote group.
• In chemical terms, Tanzanite is a hydrous calcium-aluminium
• Tanzanite colour derives from its crystallographic structure and not
to minerals present - when finely ground it produces a white
powder (i.e. it is allochromatic).
• Tanzanite's colour emerges after it has been heated at around 520°c
for 15 minutes. The colour of Tanzanite is strongly related to the
presence of vanadium and titanium in it's crystallographic
structure. Some 90% of Tanzanite production is originally found
• Tanzanite has a refractive index of 1.695 and a Moh hardness of
approximately 6.5 which makes it relatively soft for a gemstone.
• Tanzanite has a specific gravity of 3.35 g/cm³.
• In rough form, Tanzanite exhibits a phenomenon called
pleochroism - it displays 3 different colours (blue, violetish red and
greenish yellow) when looked at from different angles. These
colours are distinctive to Tanzanite.
• Tanzanite today is typically found at a depths of 80 - 100 m although the
deepest shaft is some 200 m and reserve estimations assume a
mineralisation up to at least 300 m.
• Tanzanite is found in small geological formations called boudins which in
effect are deformed, fractured veins. The geology is unique and difficult to
understand, enhancing the role of chance in the discovery process. In
addition, the Tanzanite mineralisation associated with each boudin can
• Tanzanite boudins are found embedded in graphite gneiss rock
where 10% of the rocks weight is graphite. As a result, graphite is
typically the most common and distinctive inclusion in Tanzanite.
NB. This information has been gleaned from a number of legally
validated and/or published sources. However, the author
cannot be held responsible for errors and/or omissions.