. Transactions. FeO MgO CaO NasO K2O H2O +H2O — p,o;.... 105°..105°.. MnO The analyses prove the rock to be a gabbro closely relatedto the sj^enites. The high potash percentage with the conse-quent orthoclase and biotite remind one of the gabbros atDuluth, Minn., and others in the Cortlandt series near Peeks-kill, N. Y. When recast according to the methods of thequantitative system for the classification of igneous rocks, thefollowing norms or theoretical percentages of difl:erent com-ponents are obtained: I. II. Orthoclas
. Transactions. FeO MgO CaO NasO K2O H2O +H2O — p,o;.... 105°..105°.. MnO The analyses prove the rock to be a gabbro closely relatedto the sj^enites. The high potash percentage with the conse-quent orthoclase and biotite remind one of the gabbros atDuluth, Minn., and others in the Cortlandt series near Peeks-kill, N. Y. When recast according to the methods of thequantitative system for the classification of igneous rocks, thefollowing norms or theoretical percentages of difl:erent com-ponents are obtained: I. II. Orthoclase 1 1 Albite I j- Anorthite j j Diopside ] 1 Hypersthene I | Olivine I I Magnetite j ( Ilmenite I Apatite j HjO ^ ^ * Hillebrand, W. F., The Analysis of Silicate and Carbonate Kocks, BulletinJSTo. 305, U. S. Geological Survey (1907). A TITANIFEROUS IRON-ORE DEPOSIT. 17. Fig. 1.—Fixe-Grained Gabbro, 24 Diameters ; Polarized Light ;NicoLS Crossed. Actual Field, 3 mm. Plagioclase (Pg),Orthoclase (Or), Pyroxene (Py), Magnetite (M).transactionsmining44amer
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