OPTICAL, RAMAN, AND MORPHOLOGICAL CHARACTERIZATION OF ROCK THIN SECTIONS FROM THE ARNOLD PIT FORMER TALC MINE NEAR BALMAT, NEW YORK FOR ASBESTIFORM MINERALS

This study characterized minerals in thin sections of rock samples from the former talc mining district, more specifically from the Arnold Pit, located near Balmat in northern New York using a combination of polarized light microscopy (PLM) and Raman spectroscopy. Raman spectroscopy can provide unambiguous determination of mineral species, and is particularly well suited for the discrimination of amphibole and sheet silicates. The goals were to determine micro- and bulk chemical analysis of minerals in the thin sections and to resolve possible reaction paths of mineral alterations. Also of interest was to determine the morphology of the minerals, and to ascertain if any species occurred in the asbestiform habit.

Thin sections made from two samples recently collected from the Arnold Pit were used in this study: a talc schist and an amphibole schist. PLM was used for preliminary mineralogical characterization and to distinguish crystal morphologies, and a micro-Raman spectrometer was used to capture chemical maps at specified areas on the thin section. In the talc schist, three primary phases were present: tremolite, anthophyllite, and talc. Talc forms asbestiform lamellae-like alterations within the anthophyllite grains, while tremolite remains unaltered. These lamellae-like alterations appear to form multi-step alteration halos around the talc as the anthophyllite is being altered. In the amphibole schist, talc adopts both platy and asbestiform morphologies and appears to have formed from the decomposition of tremolite.