Magnesio-arfvedsonite

Magnesio-arfvedsonite is a sodium-rich amphibole mineral, the magnesium-dominant member of the arfvedsonite series. It is not one of the six minerals named in most asbestos regulations, but it can grow in fibrous form and has been reported among the amphiboles in Libby, Montana vermiculite and in other disputed deposits.

Origin

Arfvedsonite is named for the Swedish chemist Johan August Arfwedson; the prefix magnesio- marks the magnesium-rich composition. Like other amphibole names, its boundaries are defined by the International Mineralogical Association's amphibole nomenclature and depend on detailed chemical analysis.

Significance in Asbestos Context

Magnesio-arfvedsonite is one of several sodic and sodic-calcic amphiboles that fall outside the short list of regulated asbestos minerals. That gap has been the subject of argument: a defendant may say that fibers identified as magnesio-arfvedsonite, winchite or richterite are not "asbestos" under a regulation or a contract, while plaintiffs point out that the Libby amphiboles, which include these species, caused widespread asbestosis, pleural disease and mesothelioma. Telling these amphiboles apart takes careful chemical work, usually electron microprobe or TEM with energy-dispersive X-ray analysis, and results near the boundaries between species can be named differently by different labs. For a claim, the key questions are whether the fibers were asbestiform, how much exposure there was, and whether the medical evidence shows asbestos disease, not which amphibole name a lab chose.

Example Sentence

Most of the fibers were winchite, but a few had compositions in the magnesio-arfvedsonite field.

Related Terms

Sodic Amphibole, Libby amphiboles, winchite, richterite, amphibole nomenclature, TEM-EDS, Regulated Asbestos

Notes

• Ask your expert whether an unregulated mineral name affects your claim in your state.
• Keep any lab reports that identify fiber types, with the raw chemical data if available.