Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 53 | Metric tons | NA |
| 2003 | 51 | Metric tons | -3.77% |
| 2004 | 48 | Metric tons | -5.88% |
| 2005 | 53.617000579834 | Metric tons | 11.70% |
| 2006 | 55.0359992980957 | Metric tons | 2.65% |
| 2007 | 50 | Metric tons | -9.15% |
| 2008 | 59.9339981079102 | Metric tons | 19.87% |
| 2009 | 57.6969985961914 | Metric tons | -3.73% |
| 2010 | 58.1580009460449 | Metric tons | 0.80% |
| 2011 | 53.1669998168945 | Metric tons | -8.58% |
| 2012 | 50.6049995422363 | Metric tons | -4.82% |
