Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 82084 | Metric tons, gross weight | NA |
| 2003 | 72733 | Metric tons, gross weight | -11.39% |
| 2004 | 84842 | Metric tons, gross weight | 16.65% |
| 2005 | 85000 | Metric tons, gross weight | 0.19% |
| 2006 | 85000 | Metric tons, gross weight | 0.00% |