CLAYS OF NEW YORK 613 



The loess forms an extensive deposit over a large area, not of 

 great thickness, which extends from north to sonth across the 

 state and eastward from the foothills. It is generally a very sandy 

 clay with little plasticity. Clays of similar nature to the loess 

 are fonnd underlying the river terraces in many of the broader 

 ^'alleys such as those of the Arkansas, Grand river, etc. 



The Mesozoic formations extend along the eastern edge of the 

 Kocky mountains, and also occur in some of the deeper valleys 

 tributary to the foothill belt. They consist of a great series of 

 interbedded shales, sandstones, and limestone of Jura-Trias and 

 Cretaceous age, the beds being tilted at a high angle. The Jura- 

 Trias shales have not been utilized, but the Cretaceous which over- 

 lie them have and the Tertiary or Denver beds, which carry great 

 deposits of clay, have been mined near Golden and Boulder. 



Brick clays. All of the common brick manufactured in Colorado 

 are made either from the loess or the river clays in the valleys. 



Pressed brick clays. The Cretaceous and Tertiary formations of 

 Colorado contain an abundance of clay suitable "for the manufacture 

 of pressed brick. They are mined at Golden, Boulder, and La 

 Junta. 



Fire clays and pottery clays. These two grades of clays occur in 

 close association interbedded with the Dakota sandstones, in the 

 hogbacks extending along the eastern edge of the Rocky mountains, 

 'i'he fire clay has been extensively mined at Golden, Parkdale, and 

 iQore recently at Delhi. The beds range in thickness from 4: to 

 18 feet. 



Clay products. Common bricks are manufactured at many locali- 

 ties in the state. Pressed brick are only made at La Junta, Golden, 

 Boulder and Denver. Paving bricks have been produced in small 

 (Quantities, and stoneware and sewer pipe have also been produced 

 to a limited extent. The most important clay products made in 

 (Jolorado are refractory wares, such as fire brick, locomotive 

 blocks, mufiles, scorifiers and crucibles. This is naturally one of 



