The economy of DRC relies heavily on mining. However, the smaller-scale economic activity from artisanal mining occurs in the informal sector and is not reflected in GDP data. A third of the DRC's diamonds are believed to be smuggled out of the country, making it difficult to quantify diamond production levels. In 2002, tin was discovered in the east of the country, but to date has only been mined on a small scale. Smuggling of conflict minerals such as coltan and cassiterite, ores of tantalum and tin, respectively, helped to fuel the war in the Eastern Congo.