. Bulletin of the Geological Society of America. Geology. 170 E. H. BARBOUR—SAND CRYSTALS Apparently there were great amounts of the mineralizing solution in sj^ots, and there the cr3'^stals continued to grow—a process which, if not arrested, would have cemented the sand into a,mass of The sand element in these crystals, though forming nearl}^ 60 percent of their bulk, ma}^ be considered an accident or as an inclusion, while the lime element, which is the mineralizing agent, constitutes about 40 per cent, and is the cr3'stal proper. In the fine sand, in the coarse sand, and even in the
. Bulletin of the Geological Society of America. Geology. 170 E. H. BARBOUR—SAND CRYSTALS Apparently there were great amounts of the mineralizing solution in sj^ots, and there the cr3'^stals continued to grow—a process which, if not arrested, would have cemented the sand into a,mass of The sand element in these crystals, though forming nearl}^ 60 percent of their bulk, ma}^ be considered an accident or as an inclusion, while the lime element, which is the mineralizing agent, constitutes about 40 per cent, and is the cr3'stal proper. In the fine sand, in the coarse sand, and even in the pebbles, the cal- cium carbonate, in cr3^stallizing out of solution, filled all the interstices and interspaces with cement. The calcite is comparable in a wa^^ to the connective tissue of the animal body ; dissolve all else away and yet the form is preserved by a sponge of tissue ; remove the sand from the crys- tals and the crystallographic form will be re[)resented by a sponge of cementing calcite. When immersed in acid the cement is at once attacked and the crystal quickly reduced to incoherent sand. Analyses The accompanying quantitative analyses were prepared by Messrs PI G. Woodruff and Willis-Warner, assistants in the department of geology of The University of Nebraska. The average of 4 crystals gives percent sand and per cent soluble matter. The concretions and rock give nearly identical results. Average concretions. Sand-crystal Average of four radiate sand-hnie con- cretions, Sioux county Weijrht of crystals. gr. gr. gr. Per cent of soluble matter. ;]().45 Microscopy and Crystallography Microscopic inspection, whether by transmitted or polarized light, reveals little of interest save that the cementing calcite, while showing. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appe
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