Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 6 | Thousand metric tons | NA |
| 2003 | 6 | Thousand metric tons | 0.00% |
| 2004 | 5.59999990463257 | Thousand metric tons | -6.67% |
| 2005 | 5.59999990463257 | Thousand metric tons | 0.00% |
| 2006 | 5.5 | Thousand metric tons | -1.79% |
| 2007 | 5.5 | Thousand metric tons | 0.00% |
| 2008 | 5.5 | Thousand metric tons | 0.00% |
