Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 347 | Thousand metric tons | NA |
| 2003 | 345 | Thousand metric tons | -0.58% |
| 2004 | 424.600006103516 | Thousand metric tons | 23.07% |
| 2005 | 450 | Thousand metric tons | 5.98% |
| 2006 | 450 | Thousand metric tons | 0.00% |
| 2007 | 450 | Thousand metric tons | 0.00% |
| 2008 | 450 | Thousand metric tons | 0.00% |
| 2009 | 870 | Thousand metric tons | 93.33% |
| 2010 | 857 | Thousand metric tons | -1.49% |
| 2011 | 860 | Thousand metric tons | 0.35% |
| 2012 | 860 | Thousand metric tons | 0.00% |
