MINERALOGICAL CHARACTERIZATION OF TALC ORE AND COMMERCIAL TALC PRODUCTS FROM THE GOUVERNEUR MINING DISTRICT, NEW YORK: ORIGINS OF ASBESTIFORM TALC

This study characterized the chemical composition and morphological relationships of mineral phases within outcrop and tailings rock samples and talc commercial products produced from former talc mines near Fowler and Talcville, New York. Chemical analyses of individual phases were performed by wavelength dispersive spectroscopy (WDS) and energy dispersive spectroscopy (EDS) via electron microprobe. Bulk compositional analysis was performed by X-ray fluorescence (XRF). Mineral phases were identified by powder X-ray diffraction (XRD) and polarized light microscopy (PLM) as well as WDS and EDS. Morphological features were observed by both electron and light microscopy. Detailed results are presented on one representative rock sample and one representative commercial product.

Both the outcrop samples and commercial products were micronized for bulk analysis by powder XRD and then later prepared into glass beads for XRF. The diffraction patterns show varying amounts and combinations of talc, two species of amphibole, and serpentine. Bulk compositions via XRF are almost entirely SiO₂, MgO, CaO, and H₂O (presumed from loss on ignition weight).

Polished thin sections were made from 36 rock samples. In these samples, there are three main mineral phases present: tremolite, anthophyllite, and talc. In general, tremolite exists as unaltered crystals, anthophyllite occurs as elongated minerals with acicular texture and series of fractures running perpendicular to the c-axis, and talc occurs as a fine-grained mass filling in the anthophyllite fractures and between acicular anthophyllite partings, as pseudomorphs after anthophyllite, and as platy particles. Both amphiboles species have near end member composition.

Polished grain mounts were made from 22 commercial products. The products contain tremolite, anthophyllite, and talc as well as other phases such as serpentine and some diopside. As in the rock samples, tremolite occurs as unaltered crystals and anthophyllite occurs as elongated, acicular grains, broken along the fractures that run perpendicular to the c-axis and both are of near end member composition. Talc occurs as very small particles clinging to other grains, as asbestiform grains, and as an alteration product along the rims of some minerals, including serpentine and diopside.