INTEGRATED OPTICAL, MICRO-RAMAN, AND COMPOSITIONAL ANALYSIS OF ROCK SAMPLES FROM FORMER TALC MINES IN THE GOUVERNEUR MINING DISTRICT, NEW YORK

This study uses polarized light microscopy, Micro-Raman spectroscopy, and wavelength dispersive spectroscopy (WDS) using an electron microprobe to compare the morphology and composition of tailings samples from two former talc mines in the Gouverneur Mining District, New York. The main purpose of this project was to better understand the alteration of amphiboles into talc within these samples. The interaction of these minerals along their grain boundaries is important due to the resulting asbestiform and acicular (i.e., non-asbestiform) morphologies of talc and amphiboles within the rocks in this mining district. Intensity maps created from Micro-Raman imaging highlight the different mineral phases present in the samples while the electron microprobe precisely determines the weight percent oxides of the mineral phases which aids in their identification. Backscatter electron (BSE) imaging using the microprobe was also used to compare differing mineral compositions with the Raman maps. Each mineral phase was discernable from each other through both analyses, however changes in the talc and amphibole orientations created variable intensities in the Raman maps.

The first sample is from the Arnold Pit near Fowler, New York within the mining district and is a talc schist with some tremolite and calcite. The talc occurs primarily as platy crystals and in some fine-grained masses. Compositional and morphological analyses of the minerals suggest the platy talc in this sample is an advanced alteration product of non-asbestiform anthophyllite. The fine-grained talc in this sample potentially formed from a separate hydrothermal event. The tremolite occurs as unaltered, blocky crystals. Some of the tremolite and calcite crystals are fractured without any visible alteration with fine-grained talc filling in the fractures. The second sample is from the Talcville Mine near Talcville, New York and is a tremolite schist with some crystals of anthophyllite, talc, and phlogopite. The tremolite is long, acicular, and unaltered. Phlogopite occurs as plates in the sample. Anthophyllite grains are acicular and fractured perpendicular to the long axis of the grain. Talc occurs as fine-grained masses, an alteration product along the edges of anthophyllite grains and within the fractures of the anthophyllite.