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USA | |
| [var. Labradorite] Espenshade, G. H. and Boudette, E. L., 1964, Geology of the Greenville Quadrangle Maine, US Geological Survey Quadrangle Map GQ-350. Espenshade, G. H. and Boudette, E. L., 1967, Geology and Petrology of the Greenville Quadrangle, Piscataquis and Somerset Counties, Maine, US Geological Survey Bulletin 1241-F, p F1-F60. |
| [var. Labradorite] Houston, Robert S., 1956, Genetic Study of Some Pyrrhotite Deposits of Maine and New Brunswick, Department of Development of Industry and Commerce, Augusta, Maine, pp. 117 + 6 plates. |
| [var. Labradorite] Espenshade, G. H. and Boudette, E. L., 1964, Geology of the Greenville Quadrangle Maine, US Geological Survey Quadrangle Map GQ-350. Espenshade, G. H. and Boudette, E. L., 1967, Geology and Petrology of the Greenville Quadrangle, Piscataquis and Somerset Counties, Maine, US Geological Survey Bulletin 1241-F, p F1-F60. |