Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 27444 | Metric tons, gross weight | NA |
| 2003 | 13000 | Metric tons, gross weight | -52.63% |
| 2004 | 26600 | Metric tons, gross weight | 104.62% |
| 2005 | 50400 | Metric tons, gross weight | 89.47% |
| 2006 | 70500 | Metric tons, gross weight | 39.88% |
| 2007 | 407822 | Metric tons, gross weight | 478.47% |
| 2008 | 859748 | Metric tons, gross weight | 110.81% |
| 2009 | 636482 | Metric tons, gross weight | -25.97% |
| 2010 | 801856 | Metric tons, gross weight | 25.98% |
| 2011 | 616700 | Metric tons, gross weight | -23.09% |
| 2012 | 554800 | Metric tons, gross weight | -10.04% |
