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 Photo courtesy of G. Robinson. Calcite1,017 ctBalmat, St. Lawerence County | ||
(under construction) Considered a collector gemstone because of its low hardness and easy cleavage, calcite is not suitable for wear except with extreme care. However, a faceted optical quality calcite can be quite beautiful. Pockets of Iceland spar were found in the late 1960s in New York State which yielded rhombohedral crystals over 60 cm across. Master faceter Arthur Grant of Hannibal, New York cut some of these which later became part of the gem collection of the Smithsonian Institution in Washington, D.C. as well as several other collections in major museums. In the Winter 1984 issue of Gems & Gemology, Hurlbut and Francis describe the optics resulting from the twinning commonly found in these stones combined with dispersion and high birefringence. A fantastic kaleidoscope of colors occurs as the light is broken up into progressively more pairs of rainbow rays as it crosses the twinning planes within the stones. Source: Robinson, G.W. and Chamberlain, S.C. (2007). The Gems of New York State. Rocks and Minerals, Vol. 82, No. 6, pp. 458-463. | ||
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