. Annals of the New York Academy of Sciences. Science; Science -- New York (State). 136 ANNALS NEW YORK ACADEMY OF SCIENCES of radiating crystals, the individuals increasing in size outward. There was also probably a small amount of the unknown mineral whose removal by solution left the prismatic cavities previously described. In this case, the cavities have been refilled by heulandite, but are still sharply out- lined. In other parts of the slide, quartz is giving way to heulandite, but in such cases the habit of the heulandite is different from that shown in its deposition in the open caviti
. Annals of the New York Academy of Sciences. Science; Science -- New York (State). 136 ANNALS NEW YORK ACADEMY OF SCIENCES of radiating crystals, the individuals increasing in size outward. There was also probably a small amount of the unknown mineral whose removal by solution left the prismatic cavities previously described. In this case, the cavities have been refilled by heulandite, but are still sharply out- lined. In other parts of the slide, quartz is giving way to heulandite, but in such cases the habit of the heulandite is different from that shown in its deposition in the open cavities. In fig. 11, some indication of the radiating form of the quartz can be distinguished, and outside the field the center of radiation is plainly seen. The replacement by cha])azite has taken a most irregular form, but the influence of the crystallographic character of the quartz upon its solution and removal are perceptible in Fig. 12. Replacement of quartz (clear) by heulandite (stippled). Arrows show direction of vertical axes of quartz crystals. Many of the crystallographic lines approach parallelism, but few are strictly pai-allel. X 35. Slide 77. In fig. 12, the major portion of the field is occupied by a single quartz crystal, in nearly basal section, as is shown by the interference figure. Surrounding it are other quartz crystals of various optical orientation. Eeplacement by heulandite has taken the form shown, extremely irregular but yet plainly governed more or less by differences of solubility in the quartz. Plate XI, fig. 4, illustrates one of the complex zeolitic groupings often found. Even at this stage of alteration, vestiges of the original texture of the rock and of the results of mechanical action upon it can be seen in many places. Phenocrysts of diopside are quite numerous outside of the field illnstratod. Traces of plagioclase laths can be made out, and the subcircular chlorite nodules due originally to resorption of olivine are. Please note that
Size: 1582px × 1578px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1879
