Tanzanite is an extremely rare gem that is only found in one place on Earth, and we can guess this place from its name. This place is Tanzania. Tanzanite is a variation of the mineral zoisite, which can be blue, purple, or violet in color. The famous American jewelry retailer Tiffany & Co. gave this variation of zoisite its name.
How was tanzanite formed in the Earth?
In the modern territory of Mount Kilimanjaro, a huge amount of tectonic activity took place 585 million years ago. This process caused the formation of tanzanite deposits, which are found in isoclinal folds. What happened in that period?
The first phase of the mineralization process was the forming of carbon-rich layers and their interaction with vanadium and volcanic origin formations. In Tanzania, tanzanite was found close to grossular garnets called tsavorites. Geologists say that during tectonic activity about 600 million years ago, liquid masses rich with calcium, magnesium, carbon dioxide, vanadium, zinc, and carbon trioxide were injected under high pressure and temperature into the local faults and bedrocks. In this way, zoisites (including tanzanites), tsavorites, quartz, calcite, and diopside were formed.
Why are tanzanites blue or purple?
The blue or purple color of tanzanites is due to the vanadium that is in the zoisite. Moreover, don’t forget about the pleochroism of tanzanites. What is that? Pleochroism is the ability of a mineral to change its color depending on the light. So, in cool lighting, the tanzanite is blue. However, in warm lighting, the same tanzanite can be violet or purple with a pink tint. Gemologists say that each tanzanite includes such colors as blue, violet, purple, pink, yellow, and green, and depending on the lighting, they change their colors.
Compare these minerals. All of them are zoisites.
Only tanzanites are transparent and have colors from bluish to purple. Moreover, there are several places in the world where zoisites are mined, whereas there is one unique place on Earth where tanzanites are mined.
All these gems are tanzanites:
Of course, tanzanites are the most valuable variety of zoisites.
What is the history of tanzanite discovery?
The discovery of tanzanites is connected with the name of Manuel de Souza, a Goan tailor. His second occupation was the search for new deposits of diamonds, gold, and gemstones. That is why he traveled to the most inaccessible places in Africa, where foreign people had never been. Local people named him Mad Manuel because of his passion for searching deposits of precious metals or stones.
In 1967, Manuel traveled to Arusha, a northern locale in Tanzania. He wanted to explore the place in the mountingsnear this city. The road in mountings was so hard that in some places, the local guide said that he wouldn’t go ahead. So, Manuel and 3-4 men that were with him were dropped in the wild locality. They made their camp in this place. Walking along the road, Manuel noticed some blue stones in the dust. He thought that he found a new deposit of sapphires.
As you see, the rough tanzanites have some similarities with sapphires.
But this stone was bigger and softer than a sapphire. So, he decided to register the claim to the extraction of olivine. It is unclear why because olivine is green and its appearance is different from tanzanite. But the first claim registered with the Tanzanian Government in 1967 was for extraction of olivine.
Manuel de Souza asked the famous geologist Dr. John Saul to go with him to this place. Dr. John Saul was a member of the Colored Gemstone Association in America and he owned the John Saul ruby mine in Kenya. So, this scientist was an expert in the field of gems mining. He could help in identifying new minerals that Manuel found. John’s father, Hyman Saul, was a co-owner of Luxury American Store in New York. He brought some samples of stones and showed them in the Gemological Institute of America. Gemologists concluded that these samples weren’t olivines or dumortierites. They identified them as zoisites, which contain vanadium.
Hyman had a lot of friends in the gem industry. Walter Hoving, the President of Tiffany & Co. was one of them. He fell in love at first sight when he saw this new mineral. At dinner in an Italian house in New York, Henry Platt (the owner of the steakhouse), Hyman Saul, and Walter Hoving invented the name for this new gem – tanzanite – because the name zoisite sounded too much like ‘suicide’.
Why is tanzanite a good investment?
Tanzanites are extremely rare. In the world, there is only one place where these gems are mined. This spot is the Merelani Hills in northern Tanzania. Deposits in this mine are small, so when the reserve of tanzanites are depleted, the rarity of tanzanites will become extreme.