. Carnegie Institution of Washington publication. 46 INFRA-RED TRANSMISSION SPECTRA. PREHNITE (H2Ca2Al2(SiO4)s). (Stalactitic; light green, translucent, crystalline mass; £ = mm. Curve a, fig. 32.) We have now to consider a series of hydrous silicates in which the oxygen and hydrogen are supposed to exist as such in the molecule. It will be noticed that the SiO2 radical does not give sharp bands that are in a fixed position—e. g., at ,. Prehnite has bands at , , , and , but none coincide with the water bands. It so happens that in this mineral the bands coincide very
. Carnegie Institution of Washington publication. 46 INFRA-RED TRANSMISSION SPECTRA. PREHNITE (H2Ca2Al2(SiO4)s). (Stalactitic; light green, translucent, crystalline mass; £ = mm. Curve a, fig. 32.) We have now to consider a series of hydrous silicates in which the oxygen and hydrogen are supposed to exist as such in the molecule. It will be noticed that the SiO2 radical does not give sharp bands that are in a fixed position—e. g., at ,. Prehnite has bands at , , , and , but none coincide with the water bands. It so happens that in this mineral the bands coincide very closely with those found in i 2 4- 5 6 FIG. 32. — Prehnite (a); Hydronephelite. (HNa2Al2(SiC>4)s+3H2O). (From Litchfield, Massachusetts. Massive dark-gray material ; subtranslucent in section of mm. Curve a, fig. 32.) This substance is supposed to contain water of crystallization, but the general outline of the transmission curve does not show it. Possibly it is an hydroxide. The general appearance of the material did not appear to warrant a further inquiry into this apparent exception to the rule. There is a wide band at ^. Water is expelled at a high temperature. PECTOUTE (HNaCa2(SiO3)3). (Translucent sections; / = and mm. Curves a and c, fig. 33. From Bergen Hill, New Jersey.) Curve a is for a monoclinic prismatic cleavage piece, while curve c is for a mass of needles all of which came from the same piece. The two. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carnegie Institution of Washington. Washington, Carnegie Institution of Washington
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