ARR0WP0INT8, SPEARHEADS, AND KNIVES. 875 



irretrnljir layers of impure limestone with much hornstone. Same at Lockport, 

 eastward (p. G',i). 



The first mineral is hornstone of the Pentanierons mass. This often passes into 

 translncent varieties and forms little cavities lined with chalcedony (p. 67). 



* ^ vf # X ^ ^ 



Thick-bedded dark or bluish-gray limestone with irregular cavities and often 

 silieous concretions of hornstone. This is persistent over a largo extent of country 

 (p. 87). 



* ^ *■ * * if -K 



Corniferous limestone. This rock is distinguished from the limestone below by 

 the presence of hornstone in layers or nodules, etc. In Seneca County it is in regu- 

 lar courses from 6 to 18 inches thick, usually separated by layers of hornstone and 

 sometimes embracing tlatteiied nodules of the same, which have a surface as if from 

 the crystallization of some mineral in the space between the two rocks. 



* * ^ # # * » 



In other localities these layei's of hornstone increase in number and thickness 

 almost to tlie exclusion of calcareous matter, which from weathering leaves the iiorn- 

 stone in jagged and irregular projecting points, and is locally caUed "chawed rock" 

 (p. 162). 



On the west side of the Genesee its cherty characters are better developed than 

 elsewhere. Between Caledonia and Leroy there are hundreds of acres literally 

 paved with hornstone in small angular fragments or larger masses united by carbon- 

 ate of lime (p. 158). 



The hornstone sometimes passes into chalcedony (p. 168). 



Dana' says: 



The hornstone of the Corniferous limestone is full of microscopic plants, orproto- 

 phytes, from l-.500th to l-.")000th of an inch in diameter; and with them are sponge- 

 spicules and teeth of mollusks. 



* * » 'f » # * 



The Cretaceous limestones in Texas * * * contain hornstone distributed 

 through them, like the flint through the Chaliv of England. 



The impurities iu flint marked by different colors may be peculiar to 

 certain localities. By them the prodncts of different mines have been 

 traced through their sometimes long voyages in the hands of their 

 prehistoric owners. The color of the flint from Grand Pressigny, near 

 Tours, France, is that of beeswax; that from Meudon, near Paris, is 

 nearly white; that from Spieunes, Belgium, is light-gray; that from 

 Italy, especially from the southern part, has the lustrous brown of 

 jasper and chalcedony. Of that from England, Grimes Graves is light- 

 gray, similar iu appearance to that of Spiennes; Brandon is quite 

 black; Cissbury is dark-brown, almost black, weathering out into 

 chalky whiteness. 



Of the flint from the United States, that from Illinois is light-gray, 

 weathering out to chalky-white, while that from Flint Kidge (which 

 does not weather white) passes through the entire range of color from 

 the waxy luster of brilliant chalcedony to the dull opacity of degraded 

 chert. 



' Manual of Geology, 1876. pp. 2.57 and 455. 



