Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1900 | Thousand metric tons | NA |
| 2003 | 1900 | Thousand metric tons | 0.00% |
| 2004 | 1900 | Thousand metric tons | 0.00% |
| 2005 | 1900 | Thousand metric tons | 0.00% |
| 2006 | 1900 | Thousand metric tons | 0.00% |
| 2007 | 1900 | Thousand metric tons | 0.00% |
| 2008 | 1800 | Thousand metric tons | -5.26% |
| 2009 | 1800 | Thousand metric tons | 0.00% |
| 2010 | 2100 | Thousand metric tons | 16.67% |
| 2011 | 2550 | Thousand metric tons | 21.43% |
| 2012 | 3000 | Thousand metric tons | 17.65% |
