70 GEORGE I. FIN LAY 



for hypersthene (hy), in the same porportion in which they stood for 

 diopside. 



Analysis H presents the case where after making orthoclase (or), 

 albite (ab), and acmite (ac), Na^O still rernains over. This is allotted 

 with SiOa to form sodium metasilicate (ns), NaaO . SiOa, i : i. It is 

 rarely found necessary to introduce sodium metasilicate in this way. 



Case I presents the inflexible mineral molecules ilmenite, titanite, 

 apatite, and fluorite. Sodium metasilicate is introduced, and potas- 

 sium metasihcate (ks), K^O.SiO^, as well — an extremely rare 

 occurrence. The minor inflexible molecules in the femic group are 

 magnetite, chromite, hematite, ilmenite, titanite, perofskite, rutile, 

 apatite, fluorite, calcite, and pyrite. Magnetite and hematite have 

 been introduced in preceding analyses; chromite is made in Analysis 

 S, perofskite in Analysis S, ruffle is considered in the present analysis, 

 calcite appears in Analysis O, and pyrite in Analysis K. In the 

 salic group we have the minor inflexible molecules zircon, sodalite, 

 and noselite. Zircon appears in Analysis M, and sodalite and noselite 

 in Analysis O. 



Following the order stated on p. i88, sec. 3, in the Quantitative 



Classification of Igneous Rocks, Cr2 03 not being present, we first 



allot FeO to TiOa for ilmenite (il), in the proportion 1:1. TiOa 



remaining over takes CaO and SiOj for titanite (tn), CaO.TiOj. 



SiO^, in the proportion 1:1:1. We are working with an analysis 



in which the amount of SiOa is sufficient to meet all claims upon it. 



If silica were not abundant Ti02 remaining over after the allotment 



for ilmenite would take CaO for perofskite (pf), CaO.TiOa, in the 



proportion 1:1. Such a case is given in Analysis S. Here if TiOj 



after the allotments for ilmenite and titanite still remained over, it 



would be considered as rutile (ru), T'lO^. In the next place P2O5 



takes 2)^ times as many units of CaO as there are units of P2O5, and 



CaCl 

 |- as much F or CI, for apatite (ap), 3CaO.P205H or 3CaO. 



CaF2 

 PjOgH ~ in the ratio CaO:P2 05 as 3^:1, and F or CI, to satisfy 



CaO, equal to ^PjOj. In the next place fluorine (F=26), takes ^ 

 as much CaO for fluorite (ft), CaFj. After these minor inflexible 

 molecules have been adjusted K2O is allotted for orthoclase with the 



