Industry and construction is a major and growing component of the Tanzanian economy, contributing 22.2 per cent of GDP in 2013. This component includes mining and quarrying, manufacturing, electricity and natural gas, water supply, and construction. Mining contributed 3.3 per cent of GDP in 2013. The vast majority of the country's mineral export revenue comes from gold, accounting for 89 per cent of the value of those exports in 2013. It also exports sizeable quantities of gemstones, including diamonds and tanzanite. All of Tanzania's coal production, which totalled 106,000 short tons in 2012, is used domestically.