Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 6 | Thousand metric tons | NA |
| 2003 | 6 | Thousand metric tons | 0.00% |
| 2004 | 6 | Thousand metric tons | 0.00% |
| 2005 | 6 | Thousand metric tons | 0.00% |
| 2006 | 6 | Thousand metric tons | 0.00% |
| 2007 | 6 | Thousand metric tons | 0.00% |
| 2008 | 6 | Thousand metric tons | 0.00% |
| 2009 | 8.13300037384033 | Thousand metric tons | 35.55% |
| 2010 | 7 | Thousand metric tons | -13.93% |
| 2011 | 7.5 | Thousand metric tons | 7.14% |
| 2012 | 8 | Thousand metric tons | 6.67% |
| 2013 | 8 | Thousand metric tons | 0.00% |
