FIRE TESTS OF NEW YORK BUILDING STONES 33 



mica. The quartz showed evidences of crushing. Hornblende, 

 biotite which has altered to chlorite in places, pyrite grains, zircons 

 and apatites were also noted and large crystals of red garnet are 

 common in the section. 



8 Sandstone 



Potsdam, St Lawrence co. N.Y. 



POTSDAM RED SANDSTONE CO. 

 See plate i8 



This is a quartzitic red sandstone, compact and even grained^ 

 The color varies somewhat and the bedding planes are quite promi- 

 nent. It is extensively used as a building stone. 



Under the microscope the grains appear to be well rounded; 

 many have become enlarged by a secondary growth of silica and 

 the original form of the grain is shown by a rim of limonite. The 

 stone is well cemented and in some cases the grains show complicated 

 interlocking. With the exception of a few scales of muscovite and 

 some grains of magnetite, the section is made up entireh^ of quartz 

 grains which rarely exceed .5 millimeter in diameter. 



16 Sandstone 



Oxford, Chenango co. N.Y. 



F. G. CLARKE BLUESTONE CO, 

 See plate 19 



The stone from this locality, which is used extensively as a 

 building stone, is fine grained and of a bluish gray color. 



In the thin section the rock was seen to be composed of angular 

 to rounded grains of quartz and feldspar, which in places has 

 weathered to mica. The cementing material is mostly silica, 

 though there is some calcite and some limonite. The texture is 

 quite fine, the average size of the grains being .10 millimeter. A 

 few mica scales and pyrite grains were also noted in the section. 



17 Sandstone 



Medina, Orleans co. N.Y. 



CARSON BROS. 



See plate 20 



This is a fine grained red sandstone which is quite tiniform in 

 texture and compact. It is widely used as a building stone. 



