114 now CROPS FEED. 



has a greasy feel, and in composition is a hydrous silicate 

 of magnesia. See analysis. 



Serpentine is a tough but soft massive mineral, in color 

 usually of some shade of green. It forms immense beds 

 in New England, New York, Pennsylvania, etc. It is also 

 a hydrous silicate of magnesia. See analysis. 



Chrysolite is a silicate of magnesia and iron, Avhich 

 is found abundantly in lavas and basaltic rocks. It is a 

 hard, glassy mineral, usually of an olive or brown-green 

 color. See analysis below. 



ZeoliteSi — Under this general name mineralogists are 

 in the habit of including a number of minerals wliich have 

 recently acquired considerable agricultural interest, since 

 they represent certain compounds which we have strong 

 reasons to believe are formed in and greatly influence the 

 properties of soils. They are hydrous silicates of alum- 

 ina or lime, and alkali, and are remarkable for the ease 

 with which they undergo decomposition imder the influ- 

 ence of weak acids. We give here the names and compo 

 sition of the most common zeolites. Their special signif- 

 icance will come under notice hereafter. We may add 

 that while they all occur in white or red crystallizntions, 

 often of great beauty, they likewise exist in a state of 

 division so minute that the eye cannot recognize them, 

 and thus form a large share of certain rocks, Avhich, by 

 their disintegration, give origin to very fertile soils 



