. Annals of the New York Academy of Sciences. Science; Science -- New York (State). 156 ANNALS NEW YORK ACADEMY OF SCIENCES groups have been broken up by stilbite into isolated individuals or small scattered clusters. In 101, a prehnite group is cut by veins of stilbite. In 127 (fig. 3), which was described under albite, it is found that the prehnite clusters which had been deposited upon albite are in turn giving way to natrolite. In 68, also, prehnite is being replaced by natrolite, and portions of groups have been cut off by the later mineral. The relations of prehnite and apophyllite are s
. Annals of the New York Academy of Sciences. Science; Science -- New York (State). 156 ANNALS NEW YORK ACADEMY OF SCIENCES groups have been broken up by stilbite into isolated individuals or small scattered clusters. In 101, a prehnite group is cut by veins of stilbite. In 127 (fig. 3), which was described under albite, it is found that the prehnite clusters which had been deposited upon albite are in turn giving way to natrolite. In 68, also, prehnite is being replaced by natrolite, and portions of groups have been cut off by the later mineral. The relations of prehnite and apophyllite are shown in 138. Small groups and fragments of prehnite are isolated by the apophyllite in numerous instances. The manner in which a vein of apophyllite cuts off a portion of a radiate group of prehnite crystals is illustrated in fig. 22. Calcite effects striking results. Crystals appear in the midst of preh- nite and develop in euhedral forms, which cut out areas of the earlier mineral as sharply as by a knife. This appears in slides 53, 62 and 76. ^/.o/j/ly/Z/'te. Pj-cA, Fig. 22. Prehnite cut by vein of apophyllite. X 35. Slide 138. By a continuation of the process, fragments of prehnite of extreme irregularity are left, whose outer form is determined by calcite, but through all portions of which the same fan structure prevails. Occasionally in specimens of basalt which appear to the naked eye perfectly normal and unaltered, small, shotlike nodules of prehnite are seen. The rock seems entirely impervious, and the relations are such as to make it appear that the prehnite had developed in the fused magma. This is so improbable that another explanation is naturally looked for^ and the effects seem to be very well explained by certain phenomena which appear in several of the slides, for example, 50a, 53, 65 and 118. In 50a, crusts of prehnite border areas of basalt in which the texture appears normal at first sight, but it is found that the diopside and. Please note that these images
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1879
