Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1500 | Thousand metric tons | NA |
| 2004 | 1500 | Thousand metric tons | 0.00% |
| 2005 | 1600 | Thousand metric tons | 6.67% |
| 2006 | 1500 | Thousand metric tons | -6.25% |
| 2007 | 1500 | Thousand metric tons | 0.00% |
| 2008 | 1500 | Thousand metric tons | 0.00% |
| 2009 | 1022 | Thousand metric tons | -31.87% |
| 2010 | 1055 | Thousand metric tons | 3.23% |
| 2011 | 1162 | Thousand metric tons | 10.14% |
| 2012 | 1083 | Thousand metric tons | -6.80% |
| 2013 | 1000 | Thousand metric tons | -7.66% |
