Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2005 | 430 | Thousand metric tons | NA |
| 2006 | 430 | Thousand metric tons | 0.00% |
| 2007 | 517 | Thousand metric tons | 20.23% |
| 2008 | 482 | Thousand metric tons | -6.77% |
| 2009 | 500 | Thousand metric tons | 3.73% |
| 2010 | 475 | Thousand metric tons | -5.00% |
| 2011 | 475 | Thousand metric tons | 0.00% |
| 2012 | 475 | Thousand metric tons | 0.00% |
| 2013 | 475 | Thousand metric tons | 0.00% |
