Nairobi - Tanzanian President John Magufuli on Wednesday ordered the army to build a wall around the country's tanzanite mines to prevent smuggling and better control exports of the precious gems unique to the East African country.The deep blue or royal purple stones are mined in the Mererani hills near Mount Kilimanjaro.Magufuli ordered the army to "start building a wall around this whole area," insisting the work be done as soon as possible. But he did not specify exactly where the wall should be built."Surveillance cameras will be installed and there will be only one entrance," Magufuli said. "Even if you swallow tanzanite, it will be detected".The order seems to be the latest move by Magufuli - who swept to power in 2015 on an anti-corruption platform - to regulate the mining sector, which has faced allegations of fraud and underreporting of production and profits.A commission of enquiry set up Magufuli estimated in June that $90bn had been lost in tax evasion arising from mining operations since 1998.And a parliamentary report published earlier this month revealed that smugglers and mining operators are the ones reaping the benefits of the country's tanzanite riches due to corruption and unfavourable contracts."This country is rich in natural resources. God has given us minerals which exist nowhere else but are we benefiting?" Magufuli said. "The theft of tanzanite is immeasurable. It has been going on for years and it must stop".Magufuli has locked horns with foreign mining companies, accusing them of under-valuing their production of gold, diamonds and tanzanite, resulting in a loss of billions of dollars in taxes and royalties since 1998.The Tanzanian government this month seized diamonds worth nearly $30m after accusing British company Petra Diamonds of under-estimating their value when trying to export the gems.