Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 549 | Thousand metric tons | NA |
| 2003 | 890 | Thousand metric tons | 62.11% |
| 2004 | 521 | Thousand metric tons | -41.46% |
| 2005 | 530.299987792969 | Thousand metric tons | 1.79% |
| 2006 | 530 | Thousand metric tons | -0.06% |
| 2007 | 530 | Thousand metric tons | 0.00% |
| 2008 | 530 | Thousand metric tons | 0.00% |
| 2009 | 650 | Thousand metric tons | 22.64% |
| 2010 | 600 | Thousand metric tons | -7.69% |
| 2011 | 700 | Thousand metric tons | 16.67% |
| 2012 | 700 | Thousand metric tons | 0.00% |
