Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 590 | Thousand metric tons | NA |
| 2004 | 590 | Thousand metric tons | 0.00% |
| 2005 | 740 | Thousand metric tons | 25.42% |
| 2006 | 750 | Thousand metric tons | 1.35% |
| 2007 | 780 | Thousand metric tons | 4.00% |
| 2008 | 750 | Thousand metric tons | -3.85% |
| 2009 | 600 | Thousand metric tons | -20.00% |
| 2010 | 700 | Thousand metric tons | 16.67% |
| 2011 | 700 | Thousand metric tons | 0.00% |
| 2012 | 700 | Thousand metric tons | 0.00% |
| 2013 | 700 | Thousand metric tons | 0.00% |
