MINERALOGY, LITIGATION AND ENVIRONMENTAL ENGINEERING OF TALC-ANTHOPHYLLITE-TREMOLITIC ORES FROM THE NORTHWEST ADIRONDACKS AND THE MOJAVE DESERT-WHAT ARE THEY, WHERE DID THEY COME FROM AND ARE THEY "DANGEROUS"?

In the late 1970’s, some in the mineralogical community objected to what they deemed to be the relatively simplistic US EPA/OSHA definitions of the six “things” regulated as asbestos. In the early 1990’s, the definitions were refined to emphasize the asbestiform habit of the six “things”, but concerns have arisen again for minerals with very elongate morphologies, especially transitional minerals such as talcboles, and also very fine intermixtures of talc with varying amounts of anthophyllite and/or tremolitic phases.

In NW New York, “talc” was mined from highly deformed calc-silicate rocks with very variable mineralogy and texture. The physically and chemically heterogeneous ores were then blended to achieve final bulk properties, rather than a specific mineralogical mix.

Fluid amounts and compositions; protolith compositions; and tectonics were important factors in the determination of talc, tremolite and anthophyllite amounts and morphologies. Final assemblages contained intergrowths of complexly and often incompletely retrograded asbestiform and nonasbestiform anthophyllite; pseudomorphic talc overgrowths over “remnant” anthophyllite cores; elongate talc fibers, as well as “transitional” phases.

Some have argued that the mixed/transitional amphibole/talc particles are not subject to regulation. Others have argued that the fibrous assemblage is “asbestos” or asbestiform and that in any case, elongate mineral particulates (EMP’s) warranted regulation. Similar issues are arising in the developing litigation surrounding talc ores from the Mojave Desert region where “low” amounts of asbestiform tremolitic phases occur sporadically.

Trying to reconstruct the mineralogy and hazards of the ores from decades ago is difficult. The variable product stream, coupled with the relatively sparse and non-representative remains of original products, has left a legally murky trail of just what was produced and then used in a particular exposure situation. Analytical characterizations often produce conflicting results. Litigation involving transitional and trace fibers as causative disease agents is difficult. Epidemiological and biomedical studies done without accurate identification of the chemistries, morphologies and concentrations of the mineral fibers would likely be inherently flawed.