Saniniu Kuryan Laizer, 52, found the stones weighing 9.27 and 5.1 kilogrammes (20.4 and 11.2 pounds) respectively in the northern Mirerani hills, an area which President John Magufuli had fenced off in 2018 to stop smuggling of the gem.
He sold them to the government for 7.7 billion Tanzanian shillings (nearly $3.3 million/2.9 million euros)
Tanzanite was first found in the foothills of Kilimanjaro in 1967, and the northern Tanzanian region of Manyara is the only known place where the stones, coveted by jewellers by their remarkable violet-blue sparkle, are found.
At a function celebrating the find in Manyara on Wednesday, mining minister Dotto Biteko said the stones were the biggest ever uncovered in the country.
“Laizer is our (shilling) billionaire and let us make sure that he is safe,” he said. “We are now moving from a situation where the small miners were smuggling tanzanite, and now they are following the procedures and paying government taxes and royalties