204 FreELD Museum oF NaturAL History — Greoroey, Vot. III. 
Magnesiferrous. Equally magnesic and ferrous, or nearly so. 
Me Or Seng 
Fe Oh ee 
Mir. Syllable mnemonic of magnesia and ferrous iron. 
Miric. Characterized by presence of Mg O and Fe O. 
Mirl. Syllable mnemonic of magnesia, ferrous iron, and lime. 
Mirlic. Characterized by presence of Mg O, Fe O, and Ca O. 
Mit. Syllable mnemonic of magnetite, ilmenite, and titanite, and including all 
minerals of the second subgroup of femic minerals. 
Mitic. Adjective referring to the above mentioned minerals. 
Mode. The actual mineral composition of a rock. Opposed to norm, with which 
it may or may not coincide. 


O 
Ol. Syllable mnemonic of olivine, embracing also akermanite. 
Olic. Having the proportions of, or containing, normative olivine or akermanite. 
Order. A division of Subclass based on the relative proportions of the standard 
mineral subgroups in the preponderant group. 
if 
Per- Prefix to indicate that a factor is present alone, or in extreme amount; that 
is, its ratio to another factor is > es 
Peralkalic. Extremely alkalic. Of salic minerals when K, O’ + Naz O’ is more 
than seven times CaO’. gs Ee DLC WES 
\ Ca O I 
K, O”’ + Naz O” is more than seven times Mg O + FeO + Ca O”. 
Mg O + FeO + Ca O” ck 
K, O”" + Na, O” sf 
Percalcic. Extremely calcic. Of salic minerals when Ca O’ is more than seven 
K, O’ “Na Oe 
CaO! ry) 
Of femic minerals when 
times K, O’ + Na, O’. Of femic minerals when Ca O” 
MgO +FeQ UL 

is more than seven times Mg O + Fe O. 


CaO ae 
Perfelic. Extremely felic. When normative feldspar is more than seven times the 
: L 
normative quartz or lenads. Lote < os 
Perfemane. Class V of igneous rocks, having femic minerals extremely abundant. 
Sal = I 
Festiely 275) 
Perfemic. Extremely femic. Having femic minerals more than seven times the salic. 
Sal e ah 
Fem gangs 
Perferrous. Extremely ferrous. When Fe O is more than seven times Mg O. 
Mo Gear 

Fe O = a 
