Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 160 | Thousand metric tons | NA |
| 2003 | 160 | Thousand metric tons | 0.00% |
| 2004 | 170 | Thousand metric tons | 6.25% |
| 2005 | 170 | Thousand metric tons | 0.00% |
| 2006 | 180 | Thousand metric tons | 5.88% |
| 2007 | 180 | Thousand metric tons | 0.00% |
| 2008 | 180 | Thousand metric tons | 0.00% |
| 2009 | 180 | Thousand metric tons | 0.00% |
| 2010 | 200 | Thousand metric tons | 11.11% |
| 2011 | 544 | Thousand metric tons | 172.00% |
| 2012 | 521 | Thousand metric tons | -4.23% |
