Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 35850 | Kilograms | NA |
| 2003 | 37844 | Kilograms | 5.56% |
| 2004 | 35464 | Kilograms | -6.29% |
| 2005 | 37490 | Kilograms | 5.71% |
| 2006 | 36141 | Kilograms | -3.60% |
| 2007 | 38792 | Kilograms | 7.34% |
| 2008 | 35726 | Kilograms | -7.90% |
| 2009 | 37047 | Kilograms | 3.70% |
| 2010 | 40847 | Kilograms | 10.26% |
| 2011 | 31120 | Kilograms | -23.81% |
| 2012 | 15762 | Kilograms | -49.35% |
