74 TEANSACTIONS OF THE [JaN. 23 



They also state that the molybdenite is probably graphite. 

 These minerals occur in the bunches of silicates, often of very 

 fanciful shapes, that are distributed through the limestone, 

 much as is the case with so many exposures of the same rock, in 

 the highlands of New York and New Jersey and the foothills 

 of the Adirondacks. Although the breast at Van Artsdaleu's 

 quarry is 25' high, a slab 4' square could not be obtained free 

 from these inclusions. At times they strongly suggest meta- 

 morphosed trap dikes, and certainly in their mineralogical 

 composition recall the results of contact metamorphism. In 

 the thin sections prepared from them I have been able to 

 recognize hornblende, light green pyroxene, titanite, rutile, 

 orthoclase with microperthitic albite, zircon, apatite, pyrite, 

 scapolite, and plagioclase. Of the exposures which show near 

 the quarry, No. 23 (the numbers refer to the field specimens), 

 in E2, is a vei'y coarse, and probably pegmatitic granite ; No. 22, 

 on the line between D3 and E3 is norite ; No. 6 in F2 is a decom- 

 posed gneiss ; No. 7 is a dark gneiss ; No. 8 is an ampuibolite ; 

 No. 9 contains quartz, pyroxene, and orthoclase, and has suffered 

 dynamic strains ; Nos. 10 and 11 appear to be quartzose gneiss 

 and have the peculiar blue quartz in them that is characteristic 

 of this belt ; No. 12, from the nearest exposure to the west, is a 

 decomposed mica schist. No. 7 above contains crushed qviartz 

 and feldspar, and nests of little green hornblende and biotite 

 rods that are the results of dynamic metamorphism after some 

 original bisilicate, a few decomposed cores of which remain. It 

 seems to have been a p^^'oxene. The rock has suffered severe 

 strains and crushing. The determinations of the other num- 

 bers are noted in the description of the map. Outcrops in the 

 region are none too numerous on account of the dense, veget- 

 able growth, and the high state of cultivation. The norite is 

 the most interesting of all. It might ordinarily pass for a dark 

 gneiss. The slides show with the hypersthene, green mono- 

 clinic pyroxene, hornblende, plagioclase, garnet, magnetite and 

 apatite. The hypersthene has the usual pink to green pleochro- 

 ism and parallel extinction. The monoelinic pyroxene is light 

 green, and is the same as the one which is very common in the 

 so-called norites of the Adirondacks. Garnet is in such rela- 

 tions to the bisilicates as to suggest some secondary metamorph- 

 ism. The hornblende is brown, and is far inferior to the other 

 bisilicates in amount. These minerals are very much the same 

 as those that have been described in the norites and gabbros, 

 that occur near Peekskill* in the igneous rocks of the Cortland 



* G. H. Williams, Amer. Jour. Sci. Feb, 1887, p. 135. 



