. Annals of the New York Academy of Sciences. Science; Science -- New York (State). 158 ANNALS NEW YORK ACADEMY OF SCIENCES turbidity of the pectolite in the vicinity and the manner in which the fibres disappear in the chabazite. At one point, the pectolite area is cut across by small veins of chabazite and Fig. 23. Masses of pectolite needles and isolated remuauts of same in the midst of apophyllite. X 35. Slide 129. In the hand specimen from which 86 was cut, crystals of chabazite rest upon the hemispherical surfaces of pectolite masses. In fig. 23, the replacement of pectolite by
. Annals of the New York Academy of Sciences. Science; Science -- New York (State). 158 ANNALS NEW YORK ACADEMY OF SCIENCES turbidity of the pectolite in the vicinity and the manner in which the fibres disappear in the chabazite. At one point, the pectolite area is cut across by small veins of chabazite and Fig. 23. Masses of pectolite needles and isolated remuauts of same in the midst of apophyllite. X 35. Slide 129. In the hand specimen from which 86 was cut, crystals of chabazite rest upon the hemispherical surfaces of pectolite masses. In fig. 23, the replacement of pectolite by apophyllite in 129 is sketched. Slide 135 shows practically the same relations. General Results of the First Period of Alteration In the slides which have been described, in which the minerals belong- ing to the first period of alteration are best developed, there are com- monly but obscure indications as to the nature of the original material which has been replaced. Mention has been made, however, of certain circular figures and curved lines and markings, due apparently to an insoluble residue of TiOj, etc., upon which the forces of recrystallization had no effect. These have been interpreted as survivals of an original structure in the glass. Examples are shown in Plate XI, fig. 5, Plate XII, fig. 5, and Plate XIII, fig. 2. There are instances, too, in which the secondary minerals are separated from the basalt of normal texture by a marginal band in which the texture is of much finer grain. This is believed to represent a transition between glassy crusts and more slowly cooled interiors. In all these cases the original glass has totally disap- peared, and with it such phenocrysts of diopside and plagioclase as may have been present, but in a few instances it is seen that portions of it 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
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