14 Report on Building Stone of New York. 



As a supplement to this list the " coral shell marble " near Hudson 

 and the "Lepanto " marble near Plattsburgh are here added. 



When the calcareous rock contains some serpentine the term verd- 

 antique marble is given to it. And such a marble has been quarried 

 in the town of Thurman, Warren county. 



The geological age of the crystalline limestones, which occur in the 

 State, and which are known by quarrymen as marbles, is, in some 

 cases, doubtful. The outcrops in the Highlands of the Hudson and 

 in the Adirondack region are probably all Laurentian. The belt in 

 the eastern parts of Dutchess and Putnam counties, which in its 

 northern extension is one with the Vermont marble region, is meta- 

 morphosed or altered Trenton limestone. The Westchester marbles 

 may belong in the same horizon. 



II. -SUB-CRYSTALLINE AND FRAGMENTAL ROOKS. 



1. SANDSTONES AND QUAHTZYTES. 



Sandstones are rocks made up of grains of quartzose sand, which 

 are cemented together by siliceous, ferruginous, calcareous or argilla- 

 ceous material. In some cases mica, feldspar or other minerals, are 

 mixed with the quartz sand, and then they are termed micaceous, 

 feldspathic, etc. From the nature of the cement holding the grains 

 together the rocks are variously designated as ferruginous, or iron 

 sandstone, or sometimes brownstone, as calcareous sandrock, etc. 

 The component parts may be coarse-grained or fine-grained. There 

 is an almost infinite variety in respect to shades of color, degree of 

 texture and nature of cement. And the hardness, strength, density 

 and durability are determined by these elements. Their value as 

 building material depends upon the physical constitution quite as 

 much as upon the chemical composition. Without a good bond the 

 grains fall apart and the stone is friable or crumbling. If the 

 cementing material be one which decomposes readily, as in the case 

 of some of the more argillaceous or shaly varieties, or in the calca- 

 reous sandrocks, the whole mass is soon reduced to sand. Examples 

 of sandstones, weak through such causes, are common. When the 

 quartz grains are, as it were, run together and form a kind of vitri- 

 fied mass the rock is termed a quartzyte. It looks as if the sand- 

 stone had been altered and partially fused. In some cases these 

 quart zvtes have a crystalline appearance, especially when feldspar 

 occurs with the quartz. Sandstones are found widely distributed 



