Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1500 | Thousand metric tons | NA |
| 2004 | 1500 | Thousand metric tons | 0.00% |
| 2005 | 1500 | Thousand metric tons | 0.00% |
| 2006 | 1200 | Thousand metric tons | -20.00% |
| 2007 | 1000 | Thousand metric tons | -16.67% |
| 2008 | 1000 | Thousand metric tons | 0.00% |
| 2009 | 700 | Thousand metric tons | -30.00% |
| 2010 | 483 | Thousand metric tons | -31.00% |
| 2011 | 500 | Thousand metric tons | 3.52% |
| 2012 | 450 | Thousand metric tons | -10.00% |
