Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 650 | Thousand metric tons | NA |
| 2003 | 650 | Thousand metric tons | 0.00% |
| 2004 | 650 | Thousand metric tons | 0.00% |
| 2005 | 650 | Thousand metric tons | 0.00% |
| 2006 | 650 | Thousand metric tons | 0.00% |
| 2007 | 650 | Thousand metric tons | 0.00% |
| 2008 | 360 | Thousand metric tons | -44.62% |
| 2009 | 283 | Thousand metric tons | -21.39% |
| 2010 | 189 | Thousand metric tons | -33.22% |
| 2011 | 99 | Thousand metric tons | -47.62% |
| 2012 | 78 | Thousand metric tons | -21.21% |
