FIRE TESTS OF NEW YORK BUILDING STONES 



29 



PETROGRAPHIC DESCRIPTION OF STONES TESTED 



1 Granite 



Pine Island, Orange co. N. Y. 



EMPIRE STATE GRANITE CO. 

 See plate 9 



This is a coarse grained gneissic granite of a pinkish color due 

 to an excess of pink feldspar in the stone. Quartz of a trans- 

 parent variety is next in abundance, while biotite is present in 

 small amounts and in places shows alteration to chlorite. Green 

 hornblende was also noted in the hand specimen. The stone is 

 used largely for building purposes and the smaller pieces are cut 

 into paving blocks. 



Under the microscope the feldspars were seen to be the most 

 prominent mineral. Microcline is the chief variety with some 

 microperthite, orthoclase and a little soda plagioclase. All are 

 comparatively fresh. The quartz shows many fractures. Strongly 

 pleochroic green to brown hornblende, which in places has altered 

 to chlorite and epidote, is also present. The biotite has a slight 

 greenish tinge probably due to chloritization. Ilmenite is not 

 rare and large well wedge-shaped crystals of sphene were also 

 seen. Some zircons, small apatites and pyrite grains are scattered 

 through the mass. 



Pressure phenomena are well shown, evidenced by the crushing 

 of the quartz, bending of the mica scales and fracturing of the 

 feldspar. In some of these cracks muscovite and calcite are 

 present. The crystals of the stone are well interlocked, giving 

 a firmness and compactness to the whole mass. 



2 Granite 



Garrison, Putnam co. N. Y. 



KING GRANITE CO. 

 See plate 10 



This is a fine grained gray granite used for building purposes, 

 which, in the hand specimen, shows light feldspar, smoky quartz 

 and biotite, with subordinate grains of garnet. 



In the thin section, the feldspars, which are quite fresh, were 

 seen to be orthoclase, microcline and microcline microperthite, 

 microperthite and a soda plagioclase. Deep brown to lightf bio- 

 tite is present, and has bleached in places, but jn others has altered 

 to chlorite. There are also small amounts of secondary calcite, 



