For information on how to sample and other additional information about vermiculite please see numbers 8-11 under Frequently Asked Questions. Both the EPA and Oregon DEQ recommend treating this material as an asbestos containing material. Laboratory analysis using standard PLM rarely shows asbestos contents over 1%. However, vermiculite insulation produced from Libby, Montana and marketed under the name of Zonolite has been found to contain as much as 4-7% amphibole mineral fiber using a gravity separation technique developed by the EPA that requires 3 gallons of sample. The amphibole characteristic of Zonolite is winchite, which mineralogically speaking is not technically actinolite or tremolite, or even part of the tremolite-actinolite solid solution series. However, members of the sodium-calcium rich amphibole solid solution series that includes winchite and richertite can also form solid solutions with the more magnesium-iron bearing tremolite-actinolite amphiboles. As any geologist will tell you, amphiboles are “garbage can” minerals with all kinds of variation in their chemistry. Regulations specifically state that asbestos is the fibrous form of chrysotile, amosite, crocidiolite, tremolite, anthophyllite, and actinolite. This raises the question are fibrous amphiboles that are not tremolite, actinolite or anthophyllite technically a regulated asbestos mineral? 

There is currently no data on health effects on other fibrous amphiboles not already considered regulated asbestos minerals, therefore it is prudent to consider all fibrous amphiboles to be hazardous, i.e. “asbestos’. After all, it is not the specific chemistry of the fiber but the morphology of the fiber that is the primary concern from a health risk perspective. Winchite, actinolite, tremolite, anthophyllite, and richterite have all been identified in the Libby vermiculite. The subtle differences in chemistry of some of these amphiboles makes definitive analysis by standard PLM less reliable then electron microscopy or microprobe analysis. Intergrowths of chemically different amphiboles can be included in the same fiber bundle. For this reason, BULLSEYE would prefer to report all as simply ‘fibrous amphibole’ however the test method used requires you to report tremolite, actinolite, or anthophyllite if within a certain range of optical parameters. BULLSEYE reports monoclinic fibrous amphiboles as if in the tremolite-actinolite solid solution regardless in order to avoid confusion that these fibers should not be treated as asbestos.