Transactions . erypronounced secondary action completely replaces the feldspar. 6. The age relations of the mineral constituents of the gangueis fairly simple, although the several minerals constantly overlapin their periods of generation. Plagioclase in the main, the oldestor first mineral to form, is succeeded by calcite and this in turn byquartz, although much of the calcite and even the quartz wereformed simultaneously with or even before some of the plagioclase. 7. All of the gangue minerals, plagioclase, calcite, quartz, andeven barite and celestite as well as the various metallic minera
Transactions . erypronounced secondary action completely replaces the feldspar. 6. The age relations of the mineral constituents of the gangueis fairly simple, although the several minerals constantly overlapin their periods of generation. Plagioclase in the main, the oldestor first mineral to form, is succeeded by calcite and this in turn byquartz, although much of the calcite and even the quartz wereformed simultaneously with or even before some of the plagioclase. 7. All of the gangue minerals, plagioclase, calcite, quartz, andeven barite and celestite as well as the various metallic minerals,appear to have been derived from the surrounding diabase. Thecalcite has probably been derived from the decomposition of theoriginal pyroxenic constituent as much of the plagioclase showslittle or no signs of alteration. The native silver is not only presentin association with all of the gangue minerals already mentioned,but is very commonly noticed and sometimes abundant in thediabase forming the wall Photo The Silver Lake Trail.(Brule country .
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Keywords: ., book, bookcentury1800, booksubjectmineralindustries, bookyear1895
