Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 748 | Thousand metric tons | NA |
| 2003 | 889 | Thousand metric tons | 18.85% |
| 2004 | 1042.19995117188 | Thousand metric tons | 17.23% |
| 2005 | 1050 | Thousand metric tons | 0.75% |
| 2006 | 1050 | Thousand metric tons | 0.00% |
| 2007 | 1050 | Thousand metric tons | 0.00% |
| 2008 | 1843 | Thousand metric tons | 75.52% |
| 2009 | 1679 | Thousand metric tons | -8.90% |
| 2010 | 1400 | Thousand metric tons | -16.62% |
| 2011 | 897 | Thousand metric tons | -35.93% |
| 2012 | 1000 | Thousand metric tons | 11.48% |
