Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 48 | Thousand metric tons | NA |
| 2003 | 35 | Thousand metric tons | -27.08% |
| 2004 | 51.2000007629395 | Thousand metric tons | 46.29% |
| 2005 | 34.7290000915527 | Thousand metric tons | -32.17% |
| 2006 | 38.8089981079102 | Thousand metric tons | 11.75% |
| 2007 | 40 | Thousand metric tons | 3.07% |
| 2008 | 40 | Thousand metric tons | 0.00% |
| 2009 | 37 | Thousand metric tons | -7.50% |
| 2010 | 41 | Thousand metric tons | 10.81% |
| 2011 | 46 | Thousand metric tons | 12.20% |
| 2012 | 52 | Thousand metric tons | 13.04% |
| 2013 | 52 | Thousand metric tons | 0.00% |
