. Maryland geological survey. Fig. 2.—VIEW showing flooded iron mine in the ARUNDEL formation NEAR MUIRKIRK Maryland Geological Survey 65 often septarian, and their cavities are commonly lined by brown velvetymasses of siderite crystals, which change to brown hematite on exposureto the air. The materials of the Arundel formation are so strikinglyhomogeneous, as compared with those of the underlying Patuxent andoverlying Patapsco, that its deposits have served as a datum planefor Potomac stratigraphy in Maryland, and the iron produced is prizedfor its high tensile strength. The clays are common
. Maryland geological survey. Fig. 2.—VIEW showing flooded iron mine in the ARUNDEL formation NEAR MUIRKIRK Maryland Geological Survey 65 often septarian, and their cavities are commonly lined by brown velvetymasses of siderite crystals, which change to brown hematite on exposureto the air. The materials of the Arundel formation are so strikinglyhomogeneous, as compared with those of the underlying Patuxent andoverlying Patapsco, that its deposits have served as a datum planefor Potomac stratigraphy in Maryland, and the iron produced is prizedfor its high tensile strength. The clays are commonly free from grit, but are at times sandy, and tothe landward the sand may predominate, as in the vicinity of Washing-ton. The clays are not infrequently pyritous and gypseous, both mineralscommonly occurring in druses. The gypsum druses frequently line theseptarian nodules but also occur free in the clays, as at Spring clays are in general unctuous or fat, and are an important resourcefor brick, terra cotta, an
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectpaleont, bookyear1901
