(CNN)A Chinese woman, nicknamed the 'Queen of Ivory' and thought to be one of Africa's most notorious traffickers, has been sentenced to 15 years in prison, Tanzanian authorities told CNN.

On Tuesday, a Tanzanian court found Yang Feng Glan, 70, guilty of smuggling 860 elephant tusks that authorities say are worth $6.45 million.

Yang Feng Glan, was sentenced along with her Tanzanian co-accused Salivius Francis Matembo and Manase Julius Philemon.

They were also sentenced to an additional two years in prison under Tanzania's Wildlife Protection Act, which they can convert into a fine amounting to twice the value of the ivory they are charged with smuggling. Authorities put this value at $12.9 million dollars.