Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 250 | Thousand metric tons | NA |
| 2003 | 250 | Thousand metric tons | 0.00% |
| 2004 | 250 | Thousand metric tons | 0.00% |
| 2005 | 250 | Thousand metric tons | 0.00% |
| 2006 | 250 | Thousand metric tons | 0.00% |
| 2007 | 250 | Thousand metric tons | 0.00% |
| 2008 | 250 | Thousand metric tons | 0.00% |
| 2009 | 300 | Thousand metric tons | 20.00% |
| 2010 | 250 | Thousand metric tons | -16.67% |
| 2011 | 350 | Thousand metric tons | 40.00% |
| 2012 | 320 | Thousand metric tons | -8.57% |
| 2013 | 320 | Thousand metric tons | 0.00% |
