Tanzania will allow export of gold and copper concentrates as it enters the final stages of negotiation with investors to construct a smelter in the country.
Stanislaus Nyongo, Deputy Minister for Minerals, said the government had already received a number of offers from "big investors" ready to build the smelter.
"We are working on a number of issues that investors requested before construction can begin," said Mr Nyongo.
He added that the government has received more than 20 offers from different mining firms.
The investors who have shown interests want assurance of availability of gold and copper concentrates for smelting.
Acacia Mining Plc's Bulyanhulu and Buzwagi mines produce around 50,000 tonnes of gold/copper concentrate per year.
Acacia has said it is "prepared to partner with the government to examine the possibility of viable smelting capability in Tanzania that provides employment and develops industry further."
"Technological developments may provide the key to this capability," Acacia added.
The smelter was proposed by the Presidential Mining Review Team led by Judge Mark Bomani in 2009, but the Tanzania Mineral Audit Agency (Tmaa) vetoed it on cost grounds.
But President John Magufuli, seeking more benefits for the country from its natural resources, last week ordered Mining Minister Dotto Biteko and his team to urgently work on the plan.
"We have put everything in place, from legal grounds to conducive environment for our miners," the president told Mr Biteko.
"If we have such an arrangement, it will be even easier to a monitor and obtain exact data on what was produced, how much and what was sold, for the government to get its rightful share in revenue."
If the findings of two presidential committees are accurate, the extent of the undervaluation found in Acacia's gold/copper concentrates is massive, amounting to almost $4 billion annually.
In March, 2017, President Magufuli issued a ban on exports of unrefined metals, preventing Acacia from selling partially processed gold and copper concentrates.
Acacia ceased production of gold and copper concentrates during the fourth quarter of 2017.
"All gold produced in 2018 was in doré form and was not, therefore, impacted by the current export ban on concentrate," the company said.
The mining firm has about 186,000 ounces of gold, 12.1 million pounds of copper and 159,000 ounces of silver in Tanzania which "are in a condition to be sold in the event that the concentrate export ban is lifted in the future."
According to June 2018 prices, the stockpile would have fetched $244 million after royalties.
Data from the Acacia website shows that the Bulyanhulu mine can process 1 million tonnes of underground ore per year and about 25,850 tonnes of gold and copper concentrate.
The Buzwagi mine can process 4.4 million tonnes of open pit ore per year with about 25,750 tonnes of gold and copper concentrate.
Before the export ban, the export value of gold was $1,494.1 million while overall non-traditional exports fetched $3,950.4 million in the year ending March 2017, according to Bank of Tanzania data.