New York State Museum 



LIME AND CEMENT INDUSTRIES OF NEW YORK 



ORIGIN OF LIMESTONE 



Limestones may be of either organic or chemical origin, those 

 originating in the former manner including the more extensive 

 known deposits, while the more local ones are confined chiefly 

 to the second class. 



Most surface waters contain carbonic acid and some organic 

 acids in solution, and these, in percolating through rocks con- 

 taining carbonate of lime, take the latter into solution in the 

 form of an unstable bicarbonate. On coming in contact with 

 the air, the latter is deposited either as stalactitic growths in 

 caves, or on the surface around the spring formed by the issuing 

 water. Such a deposit is known as travertin, tufa or calcareous 

 sinter. In the United States extensive deposits of this type are 

 unknown, but many local ones occur. The mammoth hot spring 

 terraces in the Yellowstone park are examples of this, and in 

 New York state deposits are found at many points, the best known 

 perhaps being the so-called " petrified marl " at Mumf ord, and 

 the tufa deposits near Clinton (N. Y.) In parts of Europe, 

 specially Italy, large deposits of tufa are also known to occur. 

 These deposits are all of fresh-water origin. 



It seems probable that the deposition of the carbonate of lime 

 may be due at times to the action of the atmosphere ; still in some 

 instances the lower forms of plant life undoubtedly play a part. 



0. A. Davis has recently shown 1 that in many Michigan lakes 

 the deposition of marl is still going on, and points out that the 

 precipitation takes place on the surface of certain small plants 

 belonging to the Characeae. 



The precipitation may be caused in two ways. 1) If the water 

 contains lime salts in excess, held in solution by carbon dioxid, 

 the former will be precipitated when the latter is taken up by 



l Jour. geol. 8: 485, 



