Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 66 | Thousand metric tons | NA |
| 2003 | 68 | Thousand metric tons | 3.03% |
| 2004 | 71.1549987792969 | Thousand metric tons | 4.64% |
| 2005 | 67.5220031738281 | Thousand metric tons | -5.11% |
| 2006 | 68.6510009765625 | Thousand metric tons | 1.67% |
| 2007 | 69 | Thousand metric tons | 0.51% |
| 2008 | 69 | Thousand metric tons | 0.00% |
| 2009 | 97.5179977416992 | Thousand metric tons | 41.33% |
| 2010 | 81.0510025024414 | Thousand metric tons | -16.89% |
| 2011 | 50 | Thousand metric tons | -38.31% |
| 2012 | 50 | Thousand metric tons | 0.00% |
| 2013 | 50 | Thousand metric tons | 0.00% |
