Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 22100 | Metric tons, gross weight | NA |
| 2003 | 37800 | Metric tons, gross weight | 71.04% |
| 2004 | 47700 | Metric tons, gross weight | 26.19% |
| 2005 | 35780 | Metric tons, gross weight | -24.99% |
| 2006 | 35000 | Metric tons, gross weight | -2.18% |
