Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1500 | Thousand metric tons | NA |
| 2004 | 1500 | Thousand metric tons | 0.00% |
| 2005 | 1600 | Thousand metric tons | 6.67% |
| 2006 | 1600 | Thousand metric tons | 0.00% |
| 2007 | 1600 | Thousand metric tons | 0.00% |
| 2008 | 1700 | Thousand metric tons | 6.25% |
| 2009 | 2619 | Thousand metric tons | 54.06% |
| 2010 | 3172 | Thousand metric tons | 21.11% |
| 2011 | 4496 | Thousand metric tons | 41.74% |
| 2012 | 3985 | Thousand metric tons | -11.37% |
| 2013 | 3432 | Thousand metric tons | -13.88% |
