KINDS OF ROCKS. 42? 



bles. f. Ferruginous; containing iron oxide and having its red color, 

 g. Concretionary; made up of concretions, h. Laminated; made up 

 of thin layers or laminae, or breaking into thin slabs, a characteristic 

 most prominent in argillaceous sandstones, i Friable ; crumbling in 

 the fingers, j. Fossinferous ; containing fossils. 



The paving stone extensively used in New York and the neighbor- 

 ing States is a laminated sandstone, of the upper part of the Hamilton 

 group in geology, quarried just south of Kingston, and at many other 

 places on the west side of the Hudson River. The rock is remarkable 

 for its very even lamination. In Western New York and in Ohio, the 

 Devonian sandstones, above the Hamilton group, together with the 

 Waverly group, afford a similar flag-stone. The " brown-stone" used 

 much in New York and elsewhere for buildings, is a dark-red sand- 

 stone from the Triassic formation, and is quarried at Portland, Conn., 

 on the Connecticut River, opposite Middletown. A lighter-colored 

 " brown-stone " or " freestone," of the same age, also much used for 

 buildings, comes from Newark, Belleville, Little Falls, and other points 

 in Central New Jersey. The handsome sandstone of light olive-green 

 tint, much employed in architecture, is from the Lower Carboniferous 

 group in New Brunswick. The soft white sandstone, in much esteem 

 among architects because so easily cut and carved, comes from Ohio 

 quarries, in beds of the Carboniferous ; it is mostly from a bed about 

 sixty feet thick, called the " Berea grit," and is obtained at Berea and 

 Independence in Cuyahoga County, and Amherst in Lorain County, and 

 elsewhere. 



Pyrite is often present in sandstones used for building, and has de- 

 faced, and is destroying, many a beautiful structure by its oxidation, 

 and the consequent decay of the rock. 



Sandstones absorb moisture most easily in the direction of the bed- 

 ding or grain, if there is any distinct bedding ; and hence the blocks, 

 when used for a building or wall, should be placed with the bedding 

 horizontal. It is, further, the position in which the stone will stand 

 the greatest pressure. 



Grindstones are made from an even-grained, rather friable sand- 

 stone, and are of different degrees of fineness, according to the work 

 to be done by them. 



Hard siliceous sandstones and conglomerates, occurring in regions of 

 metamorphic rocks, are called " granular quartz," and quartzyte (p.435). 



4. Sand-rock. — A rock made of sand, especially when not 

 of siliceous material. A calcareous sand-rock is made of cal- 

 careous sand ; it may be pulverized corals or shells, such as 

 forms and constitutes the beaches on shores off which living 

 corals and shells are abundant. 



The beach sands become cemented below high-water mark into a 

 calcareous sand-rock, which consists of layers having the pitch of the 

 surface of the beach. They are often coarse, calcareous conglomerates. 



5. Shale. — A soft, fragile, argillaceous rock, having an 

 uneven slaty structure. Shales are of gray, brown, black, 

 dull-greenish, purplish, reddish and other shades. 



