Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 9 | Thousand metric tons | NA |
| 2003 | 9 | Thousand metric tons | 0.00% |
| 2004 | 8.89999961853027 | Thousand metric tons | -1.11% |
| 2005 | 9.10000038146973 | Thousand metric tons | 2.25% |
| 2006 | 9.10000038146973 | Thousand metric tons | 0.00% |
| 2007 | 9.60000038146973 | Thousand metric tons | 5.49% |
| 2008 | 9.60000038146973 | Thousand metric tons | 0.00% |
| 2009 | 5.34499979019165 | Thousand metric tons | -44.32% |
| 2010 | 5.5 | Thousand metric tons | 2.90% |
| 2011 | 6.51999998092651 | Thousand metric tons | 18.55% |
| 2012 | 6.65299987792969 | Thousand metric tons | 2.04% |
| 2013 | 6.69999980926514 | Thousand metric tons | 0.71% |
