210 [Assembly 



The great value of graphite in this aud many other respects, 

 should prove an inducement to farmers residing near localities of 

 itj to use it on their farms ; it is found at various points through- 

 out the whole granite and gneiss region of New-Jersey, and at 

 many other localities in districts of a primitive structure. It 

 also occurs frequently in connection with veins and beds of ser- 

 pentine and other rocks of similar origin and character. When- 

 ever it can be obtained at a moderate cost, its eflfects will not fail 

 to repay the outlay, since, when finely ground, its value as a di- 

 visor for manures, would not be far below that assigned to char- 

 red peat, charcoal dust, &c., for all these purposes it would re- 

 quire to be reduced to fine powder. 



The feldspar, also, is in many respects a highly useful mineral ; 

 it is an essential ingredient of common granite, and always oc- 

 curs with it in greater or less abundance. According to Rose, it 

 consists of, 



Silica, 66 



Alumina, 18 



Potash, 14 



Lime, 1 



Oxide of iron, 1 



100 



Several varieties of this mineral are known to collectors ; of 

 these, that known as potash feldspar, (the composition of which 

 is given above,) is by far the most abundant. This mineral takes 

 its specific name from the potash, which enters so largely into its 

 composition ; it is thus called in order to distinguish it from the 

 soda feldspar, in which the potash is wholly or for the most part 

 replaced by soda, to the first of these divisions, the potash feld- 

 spar belongs he mineral occurring with the plumbago of Mor- 

 ris county. These feldspars owe their ready disintegration as 

 much to a species of chemical decomposition, as to the erosive 

 action of moisture aud changes ot temperature. Feldspars con- 

 sist of a combination of silicate of alumina, with the silicate of 

 either potash or soda ; these latter silicates are decomposed with 

 varying rapidity by the carbonic acid of the atmosphere, forming 



