Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 66300 | Metric tons, gross weight | NA |
| 2003 | 91000 | Metric tons, gross weight | 37.25% |
| 2004 | 194909 | Metric tons, gross weight | 114.19% |
| 2005 | 78915 | Metric tons, gross weight | -59.51% |
| 2006 | 73037 | Metric tons, gross weight | -7.45% |
| 2007 | 103830 | Metric tons, gross weight | 42.16% |
| 2008 | 55880 | Metric tons, gross weight | -46.18% |
| 2009 | 37105 | Metric tons, gross weight | -33.60% |
| 2010 | 40000 | Metric tons, gross weight | 7.80% |
| 2011 | 40000 | Metric tons, gross weight | 0.00% |
| 2012 | 40000 | Metric tons, gross weight | 0.00% |
