590 CX OSS, ID DINGS P IRS SON, WASHINGTON 



Orders are established as though the salic minerals were pre- 

 ponderant. This has been done for the reason that both groups 

 of minerals being present in nearly equal amounts, it is neces- 

 sary to select one group arbitrarily for the basis of division to 

 form Orders. Preference is given to the salic group because the 

 greater number of rocks belonging to this class, so far as known, 

 contain slightly more salic minerals than femic, within the range 

 of -| and J-, Moreover, the present custom of classifying these 

 rocks primarily on a basis of the feldspathic constituents may 

 be allowed to influence the choice. The division of Class III to 

 form Orders is therefore the same as those in Classes I and II. 



For Classes IV a?id V the dominant minerals are femic, and 

 the division to form Orders must be based on the relative pro- 

 portions of minerals of the first Part of this group. They may 

 be grouped into silicates, i,and non-silicates with titanosilicates, 

 2. The silicates are further divided into a) metasilicates, and 

 fr) lower silicates, as follows: 



I a) Pyroxenes, diopside, wollastonite, hypersthene, and acmite, P. 



[3) Olivine and akermanite, O. 

 2 Magnetite, hematite, ilmenite, titanite, etc., M. 



Orders in these Classes are formed by comparing subgroups 

 I and 2, the silicates and non-silicates. For adjectives to 

 describe these Orders we suggest the following syllables mne- 

 monic of the subgroups of femic minerals: pol, to indicate pyrox- 

 ene and olivine with akermanite ; mit, to indicate magnetite, 

 ilmanite, titantite and the other minerals of this subgroup. For 

 adjectives to describe Sections of Orders, based on a comparison 

 of the two parts of the silicate subgroup we suggest the sylla- 

 bles : pyr, denoting the pyroxenes, and ol, denoting olivine and 

 akermanite. 





