320 ALBERT JOHANNSEN 



the rock. Under this term are included all granites, and the light- 

 colored quartz diorites. 



Syeneid. — A noncrystalline, medium- to coarse-grained igneous 

 rock, consisting of one or more kinds of feldspar and one or more 

 members of the biopyribole group, generally biotite or hornblende. 

 The femag minerals form less than 50 per cent of the rock. Under 

 this term are included syenites, nephelite syenites, and the light- 

 colored diorites. 



There is a slight objection to this term in that the pronunciation 

 is the same as cyanide. Sinai-eid (the rock at Sinai being a true 

 syenite) might be used except for the superabundance of vowels. 

 Esseneid or Assuaneid, from the modern names for Syene, are also 

 suggested, but on the whole, on account of the common use of 

 the term syenite, it seems best to retain syeneid. 



Dioreid. — A noncrystalline, medium- to coarse-grained igneous 

 rock in which the femag mineral is an amphibole and forms over 

 half the constituents. Feldspar, of any kind, is subordinate in 

 amount. To this group belong the shonkinites, the dark-colored 

 diorites, and the hornblende gabbros. 



Quartz dioreid is a subgroup. 



Gabbreid. — A noncrystalline, medium- to coarse-grained igneous 

 rock in which the femag mineral is pyroxene and forms over 50 

 per cent. Feldspar, of any kind, is subordinate in amount. Here 

 are included the augite diorites, gabbros, and norites. 



Quartz gabbreid is a subgroup. 



Dolereid. — It is usually impossible to determine, megascopically, 

 the species of pyribole present. In such cases the term dolereid 

 may be used instead of dioreid or gabbreid. 



Quartz dolereid is a subgroup. 



Pyroxeneid. — A noncrystalline, medium- to coarse-grained ig- 

 neous rock which consists almost entirely of pyroxene. The term 

 covers the rocks now called pyroxenites. 



Amphiboleid. — A noncrystalline, medium- to coarse-grained 

 igneous rock which consists almost entirely of amphibole. It 

 includes igneous hornblende rocks, whether the hornblende is 

 primary or secondary. 



Pyriboleid. — A noncrystalline, medium- to coarse-grained ig- 



