Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 200 | Thousand metric tons | NA |
| 2004 | 200 | Thousand metric tons | 0.00% |
| 2005 | 200 | Thousand metric tons | 0.00% |
| 2006 | 200 | Thousand metric tons | 0.00% |
| 2007 | 200 | Thousand metric tons | 0.00% |
| 2008 | 200 | Thousand metric tons | 0.00% |
| 2009 | 326.635986328125 | Thousand metric tons | 63.32% |
| 2010 | 253.865997314453 | Thousand metric tons | -22.28% |
| 2011 | 230.908004760742 | Thousand metric tons | -9.04% |
| 2012 | 219.481002807617 | Thousand metric tons | -4.95% |
| 2013 | 224.386993408203 | Thousand metric tons | 2.24% |
