Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 132665 | Metric tons, gross weight | NA |
| 2003 | 248969 | Metric tons, gross weight | 87.67% |
| 2004 | 265987 | Metric tons, gross weight | 6.84% |
| 2005 | 241865 | Metric tons, gross weight | -9.07% |
| 2006 | 258087 | Metric tons, gross weight | 6.71% |
| 2007 | 253400 | Metric tons, gross weight | -1.82% |
| 2008 | 224809 | Metric tons, gross weight | -11.28% |
| 2009 | 119314 | Metric tons, gross weight | -46.93% |
| 2010 | 180000 | Metric tons, gross weight | 50.86% |
| 2011 | 323800 | Metric tons, gross weight | 79.89% |
| 2012 | 452300 | Metric tons, gross weight | 39.68% |
