Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 650 | Thousand metric tons | NA |
| 2004 | 650 | Thousand metric tons | 0.00% |
| 2005 | 700 | Thousand metric tons | 7.69% |
| 2006 | 700 | Thousand metric tons | 0.00% |
| 2007 | 700 | Thousand metric tons | 0.00% |
| 2008 | 700 | Thousand metric tons | 0.00% |
| 2009 | 680 | Thousand metric tons | -2.86% |
| 2010 | 706.700012207031 | Thousand metric tons | 3.93% |
| 2011 | 700 | Thousand metric tons | -0.95% |
| 2012 | 720 | Thousand metric tons | 2.86% |
| 2013 | 720 | Thousand metric tons | 0.00% |
