Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 75 | Thousand metric tons | NA |
| 2003 | 71 | Thousand metric tons | -5.33% |
| 2004 | 149.735000610352 | Thousand metric tons | 110.89% |
| 2005 | 150 | Thousand metric tons | 0.18% |
| 2006 | 151 | Thousand metric tons | 0.67% |
| 2007 | 151 | Thousand metric tons | 0.00% |
| 2008 | 495.212005615234 | Thousand metric tons | 227.96% |
| 2009 | 321.02099609375 | Thousand metric tons | -35.18% |
| 2010 | 313.024993896484 | Thousand metric tons | -2.49% |
| 2011 | 481.769989013672 | Thousand metric tons | 53.91% |
| 2012 | 389.140014648438 | Thousand metric tons | -19.23% |
| 2013 | 297.5 | Thousand metric tons | -23.55% |
