A Tanzanian small-scale miner has become a multi-millionaire after uncovering two of the biggest of the country's precious tanzanite stones ever found and selling them to the government.

Saniniu Kuryan Laizer, 52, found the stones weighing 9.27 and 5.1 kg 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 (about R57 427 100)

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.

"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."

The government wrote on Twitter that the stones would be placed in the national museum.