Not sure about other countries, but the in United States import of tantalum from any african country is illegal, as is the sourcing of products from African ores. This is due to the environmental impact of the mining, as well as the fact that much like "war diamonds" the funds from the mining go not to the people or the government of the country, but to local warlords. There are enough sources for tantalum that DON'T impact the environment that there's no need for african sourcecs in the US Market.