A COMPARATIVE ANALYSIS OF GARNET SAMPLES IN NEW YORK: NEW YORK CITY BEDROCK, GORE MOUNTAINS AND THE APPALACHIANS

This research involves a comparative analysis of different samples of garnet from the Appalachians and Gore Mountain, located in New York. Three samples - A, C, and D - from the Appalachian Mountains were compared with two samples - #29 and #41 - from Gore Mountain. Garnet samples collected from New York City bedrock were also used to correlate geochemical signatures among the three locations by using both whole mineral bulk oxide and representative trace element concentrations. Data was used from a geological journal of metamorphic process for the Appalachian’s samples, while an article on Barton’s garnet mining company provided the necessary data for the Gore Mountain samples. The map location for the Appalachian Mountain samples is centered on the southwestern Manhattan region of New York City in Westchester County at 41⁰ 15` N 73<sup>0</sup> 45` W, while the Gore Mountain sample map location is about 800 m on the northern side of Gore Mountain, Adirondacks, New York. Additional information, such as inclusion of metal oxides, influences variation in the properties of garnet and color and abrasiveness provide a strong basis for comparison. Results have shown that Gore Mountain garnet is of a higher abrasive quality and has a brownish tint in contrast to Appalachian samples due to the inclusion and/or higher percentages of MgO, Al₂O₃, TiO₂, and Fe₂O₃. Another contributing factor to the quality of garnet from the Gore Mountain is the observed absence of mineral zoning where overprinting, remelting, and recrystallization of minerals did not occur; unlike in the Appalachians Mountain where the three samples exhibited interior and rim data for the mineral compositions of these garnet samples. Analysis of the composition of the garnets in the pegmatitic zone of the migmatites from the Manhattan bedrock shows that they are quite different from the garnets in the immediately surrounding bedrock. This implies that the garnets in the quartzofeldspathic parts of the migmatites were not derived from the bedrock immediately adjacent to them. The three processes involved in mineral zoning are products of contact metamorphism which evidently occurred in the locations where the three samples originated from the Appalachians Mountain. Contact metamorphism was however absent in the locations where samples were taken from the Gore Mountain. Hence sample locations from the Gore Mountain only experienced regional metamorphism while the locations of the three Appalachians Mountain samples experienced regional and contact metamorphism.