Transactions . Fig. 36.—Diagrammatic sections of hypothetical ore body in limestonebeds with comnletely unsupported nuclei of original rock entirely enclo.«*edin ore. Stratification of the Islands shows that the limestone mas^^es havenot been removed from their original position. In the second case mentioned, that is, where the isolated massof unsupported rock is of a different nature from the surroundingrock, the comparatively resistant nature of the rock material hascaused it to remain either unaffected by mineralization or onlyslightly Fig. 37.—Conditions which would exist in ca-
Transactions . Fig. 36.—Diagrammatic sections of hypothetical ore body in limestonebeds with comnletely unsupported nuclei of original rock entirely enclo.«*edin ore. Stratification of the Islands shows that the limestone mas^^es havenot been removed from their original position. In the second case mentioned, that is, where the isolated massof unsupported rock is of a different nature from the surroundingrock, the comparatively resistant nature of the rock material hascaused it to remain either unaffected by mineralization or onlyslightly Fig. 37.—Conditions which would exist in ca-^o an em[)ty cavern hadbeen filled with rock debris. This would ap|>car at the l>uttom of the oremass. Also stratilication in the di^bris at varying angles to its originalposition in the country rock. Three instances of this kind can be readily citadvillc,Colo. 4()0 Retlacemext Ore Bodies—Irving 1. Quartz grains.—In the country rock of the Black Hillssilicious ores—a magnesian limestone, usually slightly marbleized—isolated grains of sand frequently occur. These have presumablybeen derived from some igneous rock, as they are filled withminute gas and other inclusions and may easily be distinguishedfrom the clear secondary silica which composes the bulk of thesilicious ore. They can only be seen, of course, with the mic
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Keywords: ., book, bookcentury1800, booksubjectmineralindustries, bookyear1895
