Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 111795 | Metric tons, gross weight | NA |
| 2003 | 137126 | Metric tons, gross weight | 22.66% |
| 2004 | 175677 | Metric tons, gross weight | 28.11% |
| 2005 | 194421 | Metric tons, gross weight | 10.67% |
| 2006 | 195000 | Metric tons, gross weight | 0.30% |
