. Annals of the New York Academy of Sciences. Science; Science -- New York (State). FENNER, THE WATCHVNG BASALT 137 plentiful. There are many fracture-lines, into some of which a reddish- brown deposit of sand and clay has been carried from the underlying lake beds. Most of the slide is in the stage of recrystallization in which zeolites are prominent, but in places has advanced to the stage of calcite and kaolin. Stilbite and analcite can be recognized, and others may be present. In the illustration, the radiating groups somewhat simulating forms of vegetation are probably crystals of quartz
. Annals of the New York Academy of Sciences. Science; Science -- New York (State). FENNER, THE WATCHVNG BASALT 137 plentiful. There are many fracture-lines, into some of which a reddish- brown deposit of sand and clay has been carried from the underlying lake beds. Most of the slide is in the stage of recrystallization in which zeolites are prominent, but in places has advanced to the stage of calcite and kaolin. Stilbite and analcite can be recognized, and others may be present. In the illustration, the radiating groups somewhat simulating forms of vegetation are probably crystals of quartz surviving from a much earlier period. They appear to branch from minute cracks. In some por- tions of the slide they show strongly the effects of solution. As regards the replacing mineral, it is not possible to be more specific than to say that it is probably a zeolite. In 125, quartz crystals which have begun. Fig. 13. Replacement of quartz by calcite. The quartz has the fan structure generally supposed to be typical of vein quartz, but it has probably replaced basalt. The granular-looking calcite sho^YS features which are plainly a survival of those in the quartz. X 35. Slide 5S. their growth in similar groups radiating from cracks have reached a large size. In slide 58, a dense, normally crystalline basalt is crusted with quartz and chalcedony. The quartz has the fanlike crystallization supposed to be typical of vein quartz, although certain circular lines and markings (similar to those shown in fig. 2, though not so pronounced) suggest that much of the quartz may have replaced a glassy crust of basalt. The chalcedonic SiOj has a fibrous appearance and negative elongation. Within the basalt, the normal texture is preserved, but with crossed nicols it is seen that in places both diopside and plagioclase have been replaced by a mosaic of quartz. In the outer crusts, calcite in a finely granular form is working in and replacing the quartz. It is developed most. Please note tha
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1879
