Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 226 | Thousand metric tons | NA |
| 2004 | 272 | Thousand metric tons | 20.35% |
| 2005 | 263 | Thousand metric tons | -3.31% |
| 2006 | 306 | Thousand metric tons | 16.35% |
| 2007 | 351 | Thousand metric tons | 14.71% |
| 2008 | 330 | Thousand metric tons | -5.98% |
| 2009 | 330 | Thousand metric tons | 0.00% |
| 2010 | 330 | Thousand metric tons | 0.00% |
| 2011 | 330 | Thousand metric tons | 0.00% |
| 2012 | 330 | Thousand metric tons | 0.00% |
