Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2543 | Thousand metric tons | NA |
| 2003 | 2783 | Thousand metric tons | 9.44% |
| 2004 | 2914 | Thousand metric tons | 4.71% |
| 2005 | 2000 | Thousand metric tons | -31.37% |
| 2006 | 1700 | Thousand metric tons | -15.00% |
| 2007 | 1700 | Thousand metric tons | 0.00% |
| 2008 | 1700 | Thousand metric tons | 0.00% |
| 2009 | 1700 | Thousand metric tons | 0.00% |
| 2010 | 1700 | Thousand metric tons | 0.00% |
| 2011 | 1700 | Thousand metric tons | 0.00% |
| 2012 | 1700 | Thousand metric tons | 0.00% |
| 2013 | 1700 | Thousand metric tons | 0.00% |
