868 T^EW YORK STATE MrSEUM 



An average analysis^ of the Iron Clad brand shows : 



SiO.. 21.5 



^^A I 10.5 



FeA ) 



CaO 63.5 



MgO- 1.8 



KgOandXa^O .4 



SO3 1.5 



Sand cement is also mannfactnred at these works, and is dis- 

 cussed briefly later in this paper. 



Helderberg^ cement co. The plant of this company is located at 

 Howe Cave, Schoharie co. Quarries in the Waterlime group at 

 this point have been long used for the manufacture of natural 

 cement, while quarries higher up, both geologically and topo- 

 graphically, furnished a very pure limestone which was burned 

 into lime. 



In 1898, the Helderberg cement co. began to utilize the stone 

 from these latter quarries in the manufacture of Portland cement. 

 Commenced on a small scale, the industry would seem to have 

 promised favorable results, as a much larger plant, belonging to 

 the same company, was erected during 1900. The new plant has 

 a nominal capacity of 1600 barrels a day. The materials used 

 are limestone and clay. 



As noted above, the limestone used for Portland cement is ob- 

 tained from the old lime quarries, and the clay from a deposit 

 in the vicinity. Smidth ball mills and Davidsen tube mills are 

 used for crushing, reducing and mixing the materials. The wet* 

 process is employed and 12 rotary kilns are in use. The result- 

 ing clinker is ground in ball mills and tube mills, and the product 

 is marketed as the " Helderberg " brand. 



The various quarries at Howe Cave show exposures of the dif- 

 ferent formations from the Clinton up to the Pentamerus. Dr 



1 Lewis, F. H. Min. ind. 6: 97. 



