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R. J. COLONY 



been totally destroyed. Such relations are shown in the old 

 Mahopac, Tilly Foster, O'Neill, Forshee, Redback, Standish, 

 Croft, and Todd mines in Orange and Putnam counties. New York. 

 It seems evident, therefore, that the injection of an igneous 

 mass into pre-existing rock, and its subsequent consolidation, sets 

 into motion physical and chemical processes which produce a 



Fig. 12 



Fig. II. — Photomicrograph of Pochuck granite, Clove Mine, Orange County, 

 New York. Nicols crossed, magnification 20 diameters. The gray field is a large 

 unit grain of quartz. Swamped in the quartz is a serpentinized remnant of Pochuck- 

 Grenville, consisting of an orthorhombic pyroxene with attached and sericitized 

 feldspar. Practically all of the minerals other than quartz are simply remnants of 

 partially assimilated fragments of like type, all profoundly affected by the magmatic 

 end-stage aqueo-igneous solutions which gave birth to the quartz. 



Fig. 12. — Photomicrograph of Pochuck granite, Forest of Dean Mine, Orange 

 County, New York. Nicols crossed, magnification 20 diameters. An extremely 

 coarse, grayish- white granite made up of end-stage quartz and feldspar with partially 

 assimilated fragments of Pochuck-Grenville. The gray field is quartz, the fragments 

 are remnants of country rock. 



startling array of progressive changes,^ both in the parent body 

 and in the rock invaded. In many cases the effects are profound 

 and of the utmost economic importance, since not only are most 

 metalliferous deposits connected directly or indirectly with such 

 processes, but many substances used in the arts and industries 

 have their origin in the same sources. 



^ A recent article by Bo wen on the behavior of inclusions in igneous magmas, 

 which appears in a supplement to Journal of Geology, No. 6, Vol. XXX (1922), deals 

 with some of the changes, which are explained on the basis of the "reaction principle." 



