. Annals of the New York Academy of Sciences. Science; Science -- New York (State). FENNER, THE WATCHUNG BASALT 171 hematite, while the areas thus outlined have the form of chabazite, al- though wholly occupied by interlocking natrolite crystals. In 94 also, natrolite is seen to be advancing across chabazite. Several hand specimens show a distinctive method of replacement of chabazite by laumontite. The laumontite appears to start from some nucleus within a solid crystal of chabazite and grow in radial crystals, until there may be only a crust of chabazite left. Slide 147 contains several radi
. Annals of the New York Academy of Sciences. Science; Science -- New York (State). FENNER, THE WATCHUNG BASALT 171 hematite, while the areas thus outlined have the form of chabazite, al- though wholly occupied by interlocking natrolite crystals. In 94 also, natrolite is seen to be advancing across chabazite. Several hand specimens show a distinctive method of replacement of chabazite by laumontite. The laumontite appears to start from some nucleus within a solid crystal of chabazite and grow in radial crystals, until there may be only a crust of chabazite left. Slide 147 contains several radial groups of this kind. In 77 also, there is replacement of chabazite by laumontite, though in neither of the thin sections does the evidence appear as decisive as in large Fig. 28. Needles of natrolite which have penetrated areas of stilbite. Slide 121. X 35. In 120 and 138, there is an association of laumontite and heulandite. The relations are not as clear as might be desired, but laumontite appears later. Replacement of all three minerals by caleite is seen in numerous in- stances. It appears that chabazite, heulandite and stilbite followed each other in this order and that they were all earlier than natrolite, caleite and laumontite. Laumontite Because of the friable nature of laumontite, it was found difficult to get ^ood microscopic sections showing it. There are only a few, therefore, which illustrate its occurrence, and in these the relations rarely appear of a decisive nature. On the other hand, fortunately, it is one of the few minerals which occur in the large specimens in such a manner as to make the sequence beyond question. It is frequently seen resting upon drusy. 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 New York Academy of Sciences; Casey, Thos. L. (Thomas Lincoln), 1857-1
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