MODE VII. SAUSSURITE. 357 



black base, marked with white and green spots, 

 has been taken for a lava by many naturalists, 

 among others by Mr. Ferber."* 



That the cornienne is a term which ought to 

 be dismissed from mineralogy, will sufficiently 

 appear from the following description, by Brong- 

 niart, a very industrious and exact mineralogist. 



" Corn&nne^ is a rock very difficult to deter- 

 mine, and still more difficult to confine to pre- 

 cise limits. On one side it approaches very 

 near to wacken, and on the other to argillaceous 

 schistus : it has besides numerous relations with 

 basalt, and even with amphibolc, or hornblende. 



" This rock is generally compact and solid ; 

 its fracture is dull, rather even, but irregular; it 

 yields by breathing on it a very sensible argil- 

 laceous odour; it is generally difficult to break, 

 causing the hammer to rebound, and presenting 

 a kind of tenacity, which throws it at a distance 

 from wacken, and approaches basalt. It often 



* Journal de Physique, 1794, p. 258. 



" f Corneus. Wall. This genus contains the greater part of our 

 tmphibole hornblendes. Corne'enne rock, Haiiyj omitting the va- 

 rieties 2, 3, and 4 vulgarly pierre de come. 



<( This species must not be confounded with the hornstein of the 

 German mineralogists: it has been seen that this was a silex. 

 Corneenne must also be distinguished from the roche de corne of 

 Saussure, which seems to be a trap rock, in the acceptation that we 

 give to that word, according to Mr. Werner." 



