Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 20018 | Metric tons, gross weight | NA |
| 2003 | 18318 | Metric tons, gross weight | -8.49% |
| 2004 | 24857 | Metric tons, gross weight | 35.70% |
| 2005 | 22672 | Metric tons, gross weight | -8.79% |
| 2006 | 26710 | Metric tons, gross weight | 17.81% |
