MINERALOGICAL CLASSIFICATION OF IGNEOUS ROCKS 85 



Qh 



Class 1, Order 1, Family 8; Class 4, Order 2, Family 2; and 

 Class 4, Order 2, Family 10. Numbers in bold-face type in the 

 list indicate proper families among scattered (misnamed) rocks. 



The rocks may seem rather scattered, but upon careful com- 

 parison it will be seen that they are not so far apart as they appear 

 at first sight, for the lighter and darker rocks of Classes 2 and 3 

 in the gabbro and 

 diorite families and of 

 Classes 1 and 2 in 

 the granite, syenite, 

 monzonite, etc., fam- 

 ilies have ordinarily 

 not been separated in 

 petrographic reports. 

 Much of the variation, 

 of course, is due to 

 the loose naming of 

 rocks, and an andesine- 

 bearing rock with Kf 

 augite may have been 

 named gabbro, and a 

 mesocratic labradorite- 

 augite rock, diorite, etc. 

 Thus the basalts in the 

 list below — 2315(4), 



3 2I 5(!), 33i5(5)— in- 

 clude 9 rocks belonging 

 to Order 3, Family 15, 

 the normal gabbro- 

 basalt family, 4 of the 

 rocks being mesocratic Fig. 23.- 

 and 5 melanocratic- 



The remaining rock (3215) is a melanocratic andesine-bearing 

 rock which should have been called an andesite. 



Andesite 2215(6), 3215(1). 

 Aplite 128(3), 217(1), 223(1). 

 Alaskite 118(2), 117(2), 128(1). 



,Caf 



Folds 

 -Rocks of Order 4 falling in Classes 1 to 3 



