Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 3190 | Thousand metric tons | NA |
| 2004 | 5600 | Thousand metric tons | 75.55% |
| 2005 | 4575 | Thousand metric tons | -18.30% |
| 2006 | 4300 | Thousand metric tons | -6.01% |
| 2007 | 4300 | Thousand metric tons | 0.00% |
| 2008 | 4300 | Thousand metric tons | 0.00% |
| 2009 | 4300 | Thousand metric tons | 0.00% |
| 2010 | 5490 | Thousand metric tons | 27.67% |
| 2011 | 4210 | Thousand metric tons | -23.32% |
| 2012 | 1950 | Thousand metric tons | -53.68% |
| 2013 | 6600 | Thousand metric tons | 238.46% |
