Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 20 | Thousand metric tons | NA |
| 2003 | 20 | Thousand metric tons | 0.00% |
| 2004 | 165.416000366211 | Thousand metric tons | 727.08% |
| 2005 | 190.231994628906 | Thousand metric tons | 15.00% |
| 2006 | 267.760009765625 | Thousand metric tons | 40.75% |
| 2007 | 255.5 | Thousand metric tons | -4.58% |
| 2008 | 255.5 | Thousand metric tons | 0.00% |
| 2009 | 154.550003051758 | Thousand metric tons | -39.51% |
| 2010 | 143.11799621582 | Thousand metric tons | -7.40% |
| 2011 | 162.983993530273 | Thousand metric tons | 13.88% |
| 2012 | 157.843994140625 | Thousand metric tons | -3.15% |
| 2013 | 162.660995483398 | Thousand metric tons | 3.05% |
