Amphibole Asbestos From Libby, Montana: Aspects of Nomenclature
A G. Wylie, Jennifer R. Verkouteren
Richterite-asbestos and winchite-asbestos are not listed in the Federal regulations governing asbestos. However, asbestiform winchite is found in the gangue at the Libby, Montana, vermiculite deposit, where asbestos-related diseases have been reported among the miners and millers. Changing amphibole nomenclature, uncertainties in Fe+2/Fe+3, and natural compositional variability result in samples of the asbestiform amphibole from Libby being variably classified as soda tremolite, richterite, sub-calcic actinolite, and winchite. A classification of winchite-asbestos is assigned for two samples of Libby asbestos analyzed for this report, consistent with the most recent IMA classification system. While some of the unit cell parameters and optical properties reported here are distinctive, others are very similar to the tremolite-actinolite series. Both richterite and winchite are known to occur as asbestos and as such, should be included in the Federal asbestos regulations.