Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 506 | Thousand metric tons | NA |
| 2003 | 507 | Thousand metric tons | 0.20% |
| 2004 | 558.987976074219 | Thousand metric tons | 10.25% |
| 2005 | 630 | Thousand metric tons | 12.70% |
| 2006 | 630 | Thousand metric tons | 0.00% |
| 2007 | 650 | Thousand metric tons | 3.17% |
| 2008 | 1193 | Thousand metric tons | 83.54% |
| 2009 | 1162 | Thousand metric tons | -2.60% |
| 2010 | 1347 | Thousand metric tons | 15.92% |
| 2011 | 1666 | Thousand metric tons | 23.68% |
| 2012 | 1600 | Thousand metric tons | -3.96% |
