334 NEW YORK STATE MUSEUM 



typical and characteristic ; except that they contain green mono- 

 clinic pyroxene instead of either hornblende or biotite, or else this 

 in association with hornblende. Their acid character, possessing as 

 they often do, much quartz, causes them to depart from the gabbro 

 types. Especially towards the great masses of gabbro and anortho- 

 site, gneissoid rocks appear that are difficult to classify in their 

 stratigraphical relations. They contain abundant plagioclase, augite, 

 hornblende and deep pink garnets and are probably gneissoid forms 

 of gabbro. Still the relations are much confused. Towards the 

 contacts, pegmatite masses are also met at times of great size, but 

 they are better shown in adjoining towns. 



Petrography of the limestones and associated black schists. 

 In thin sections the pure white limestones show little of interest. 

 They contain flakes of graphite, small scales of phlogopite, an occa- 

 sional apatite crystal and little else. Such occur at the furnace 

 quarry on the ridge just north of Port Henry ; below this along the 

 lake shore ; and south of the Pilfershire Mine. 



The limestone afforded is a 'very pure calcium carbonate at the 

 first mentioned locality. It has yielded some unique crystals of cal- 

 cite. Often closely associated with this latter is the mottled serpen- 

 tinous limestone or ophicalcite. Its best exposures are in the belt 

 along the ridge from a point north of the Cheever Mine and thence 

 southward to the Lee Mine. Quarries have been opened at several 

 points. It outcrops again west of Moriah Center, on the present 

 road to North Hudson, and also on the old and now abandoned 

 highway, nearly due north of Ensign Pond. The rock is a dolomi- 

 tic marble with copious green mottlings of serpentine. At times 

 these are evenly distributed and a quarter inch across as a maximum, 

 and then the stone is very beautiful, when polished, but such 

 pieces can seldom be obtained of large size or of even texture. 

 The masses of serpentine too often form great blotches, up to sev- 

 eral inches across, and mar the appearance of the stone. Small 

 bunches of silicates also appear and afford white pyroxene, brown 

 tourmaline, rose quartz, beautiful crystals of brown hornblende, 

 titanite, etc., as later set forth. Similar serpentinous marbles have 

 in Warren county afforded specimens thought to be Eozoon, as 

 described by A. M. Edwards (Proc. Lyceum Nat. Hist. 1ST. Y., 1870, 

 p. 96). G. P. Merrill has also written of them and is able to show 



