Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1080 | Thousand metric tons | NA |
| 2004 | 1000 | Thousand metric tons | -7.41% |
| 2005 | 1100 | Thousand metric tons | 10.00% |
| 2006 | 1100 | Thousand metric tons | 0.00% |
| 2007 | 1000 | Thousand metric tons | -9.09% |
| 2008 | 1000 | Thousand metric tons | 0.00% |
| 2009 | 3900 | Thousand metric tons | 290.00% |
| 2010 | 3600 | Thousand metric tons | -7.69% |
| 2011 | 3600 | Thousand metric tons | 0.00% |
| 2012 | 3440 | Thousand metric tons | -4.44% |
