REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1900 rl67 



A mica diorite of the Cortlandt series was tested^ for com- 

 pressive strength, crushing at 20,250 lb a square inch. 



Newark diabase 

 The " trap " of the Newark system has been long known as a 

 valuable road metal. Large quarries (40) in this rock are located 

 north of Nvack, Rockland co.; while a quarry (41) has been 

 recently opened near Mt Ivy, Rockland co. Tests of material 

 from several of these quarries will be found recorded on p. 

 rl4-r22 of this volume. 



SANDSTONES : INCLUDING SHALES 



Poughquag quartzite 



In Westchester county the Poughquag quartzite is a very 

 liard and compact siliciously cemented sandstone, occurring at 

 the contact between the Fordham gneiss and Stockbridge lime- 

 stone. The formation has a thickness of at least 30 feet near 

 Hastings but thins out on going south or east. The rock is pre- 

 vailingly light colored and very evenly and thinly bedded, the 

 slabs varying usually from J inch to 2 inches in thickness. This, 

 with the closeness of its jointing, usually prevents even moder- 

 ate sized blocks from being obtained. The rock therefore, 

 though highly durable, is of little economic importance. It has 

 been used however as coping for a retaining wall on Warburton 

 avenue near Hastings. At this point it was obtained in slabs 

 about 4 feet by 3 feet by 3 inches and makes an ideal coping. 



Near Adams Corners in Putnam county is a small quarry in 

 this formation (43). One of the openings, now almost hidden by 

 vegetation, is shown on pi. 55. The product was used for fur- 

 nace lining. 



Hudson shales and sandstones 



Prof. William B. Dwight states that in Dutchess county the 

 sandstone of the Hudson formation is everywhere fine grained 

 and very irregularly bedded; and that it is of only local use as 

 building stone. Quarries in the thicker beds have been worked 

 near Highland, Ulster co.; and the shales of the formation have 

 been quarried to some extent in Orange county for use as road 

 metal. 



•Newberry. School of mines quarterly, July 1887. 



