Proceedings of the United States National Museum . figure 12. The prism faces gave goodmeasurements indicating the prismatic angle to be 80° 59. Thefront pinacoid also gave good signals butthe side pinacoid (010) is etched dull. Thebase is horizontally striated as crossed nicols these crystals gavethe pattern shown in figure 19. Althoughat first glance appearing more complicated,this is found to be only a variation of thestructure shown in figure 18, and is capableof the same interpretation. These interpretations are applicable onlyto the prehnites here described and thismine
Proceedings of the United States National Museum . figure 12. The prism faces gave goodmeasurements indicating the prismatic angle to be 80° 59. Thefront pinacoid also gave good signals butthe side pinacoid (010) is etched dull. Thebase is horizontally striated as crossed nicols these crystals gavethe pattern shown in figure 19. Althoughat first glance appearing more complicated,this is found to be only a variation of thestructure shown in figure 18, and is capableof the same interpretation. These interpretations are applicable onlyto the prehnites here described and thismineral seems to adopt numerous other con-fused intergrowths producing other effectsas shown by the discussions of Mallard andEmerson abstracted in Danas Mineralogy. The green prehnite from one of the sheetedveins was purified for analysis and analyzedin the Museum laboratory yielding the resultsgiven in column 1 below. In column 2 arequoted the results obtained on analysis ofprehnite from Admiralty Inlet, and in column3 the theoretical
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Keywords: ., bookauthorun, bookcentury1800, bookdecade1870, booksubjectscience
