Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 0.616999983787537 | Thousand metric tons | NA |
| 2012 | 0.541999995708466 | Thousand metric tons | -12.16% |
| 2013 | 0.5 | Thousand metric tons | -7.75% |
