Mineral-rich African states have been deprived of huge sums of royalties and taxes by mining firms, a report says. The report, by prominent development charities, blames a lack of legislative oversight and excessively generous tax concessions agreed with the firms. It says some mining companies have also avoided paying tax through secret contracts with African governments…The report says the lost revenues could have been used for development...Even in the boom times, African nations failed to profit as much as they should have done from natural resources...