Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 450 | Thousand metric tons | NA |
| 2003 | 520 | Thousand metric tons | 15.56% |
| 2004 | 470 | Thousand metric tons | -9.62% |
| 2005 | 550 | Thousand metric tons | 17.02% |
| 2006 | 600 | Thousand metric tons | 9.09% |
| 2007 | 600 | Thousand metric tons | 0.00% |
| 2008 | 800 | Thousand metric tons | 33.33% |
| 2009 | 800 | Thousand metric tons | 0.00% |
| 2010 | 1100 | Thousand metric tons | 37.50% |
| 2011 | 820 | Thousand metric tons | -25.45% |
| 2012 | 800 | Thousand metric tons | -2.44% |
