444 



REPORT ON NATION AL MUSEUM, 1886. 



Sandstones are not in all eases composed wholly of quartz grains, 

 but frequently contain a variety of minerals. The brown Triassic sand- 

 stones of Connecticut, New Jersey, and Pennsylvania are found, on 

 microscopic and chemical examination, to contain one or more kinds of 

 feldspar and also mica (see Fig. G, Plate n), having, in fact, nearly the 

 same composition as a granite or gneiss, from which they were doubtless 

 originally derived. According to Dr. P. Schweitzer,* a tine-grained 

 sandstone from the so-called Palisade range in New Jersey contains from 

 30 to 60 per cent, of the feldspar albite. That quarried at Newark, in 

 the same State, contains, according to his analysis, albite, 50.40 per- 

 cent, j quartz, 45.49 per cent. ; soluble silica, .30 per cent. ; bases solu- 

 ble in hydrochloric acid, 2.19 per cent., and water, 1.14 per cent. Iron 

 pyrites is a common ingredient of many sandstones. Unless quite 

 abundant the chief danger to be apprehended from the use of such 

 stone is the change of color it is liable to undergo on exposure through 

 its oxidation. 



Sandstones are of a great variety of colors; light gray (almost white), 

 gray, buff, drab or blue, light brown, brown, pink, and red are common 

 varieties, and, as already stated, the color is largely due to the iron 

 contained by them. According to Mr. G. Mawt the red and brownish- 

 red colors are due to the presence of iron in the anhydrous sesquiox- 

 ide state, the yellow color to iron in the hydrous sesquioxide state, and 

 the blue and gray tints to the carbonate or the protoxide of iron. It is 

 also stated that the blue color is sometimes caused by finely-dissemi- 

 nated iron pyrites, and rarely by an iron phosphate-! (See page 30G.) 



Sandstones vary in texture from almost impalpably fine-grained 

 stones to those in which the individual grains are several inches in 

 diameter. These coarser varieties are called conglomerates , or, if the 

 grains are angular instead of rounded, breccias. Neither of these varie- 

 ties are at present quarried in this country to any great extent, though 

 in foreign countries calcareous breccias form some of the most beautiful 

 marbles. 



All sandstones, when freshly quarried, are found to contain a vari- 

 able amount of water, which renders them soft and more easily worked, 

 but at the same time peculiarly liable to injury by freezing. So pro- 

 nounced is this character that many quarries in the northern regions 

 can be worked only in the summer months, as during the cold season 

 the freshly quarried material would freeze, burst, and become entirely 

 ruined. It is customary also for dealers to refuse to assume any risks of 

 injury from freezing to which such stone may be liable after shipment. 

 After the evaporation of this " quarry water,' 7 as it is called, the stone 

 is found to be considerably harder, and hence more difficult to work. 

 This hardening process is explained by Newberry and others by the 



* American Chemist, July, 1671, p. 23. 



t Quar. Jour. Geol. Soc. of Loudon, xxiv, p. 355. 



t Notes on Building Construction, Part in, p. 35. 



