Classification of Massive Rocks. 297 
B. THE QUARTZLESS PORPHYRIES. 
The quartzless porphyries are the old effusive equivalents of the 
syenites. They are porphyritically developed with an alkaline feld- 
spar and one or more of the iron-bearing silicates as porphyritic 
crystals. Their ground mass is holocrystalline, consisting principally 
of feldspar and quartz. They are subdivided into :— 
1. ORTHOPHYRE, containing a monoclinic alkaline feldspar among 
the porphyritic crystals. 
(A) biotite-orthophyre, containing in addition porphyritic 
biotite. 
(B) amphibole-orthophyre, with amphibole in porphyritic 
stals 
crystals, 
(c) augite-orthophyre, with ‘augite as the prominent por- 
phyritic constituent. i 
2. RHOMBIC-PORPHYRY. This rock is characterized by the rhom- 
_boidal shape of its porphyritic feldspars, which 
belong to the anorthoclase series. 
3. KERATOPHYRES, contains a sodium-rich alkaline feldspar, and 
ti | t yp pl y iti lly developed. Amo 
the bisilicates a malacolitic augite is most promi- 
nent. The keratophyres include :— 
(A) keratophyre, in which are no porphyritic quartzes. 
(B) quartz-keratophyre, in which quartz is porphyritically 
developed. 
C. THE PORPHYRITES. 
The porphyrites correspond to the diorites of the intrusive class. 
hey are characterized by the possession of plagioclase and horn- 
blende, together with a dark mica or pyroxene, and sometimes 
quartz, as their principal components. They are porphyritic, but 
their ground mass may be either holocrystalline, felsitie or amor- 
phous in character, They are divided in accordance with the nature 
of the predominating iron-bearing constituent, which occurs along 
with the plagioclase in porphyritic crystals, into :—, 
1. MICA-PORPHYRITES, containing biotite as their principal iron- 
bearing porphyritic constituent, including :— 
(A) mica-porphyrite, which contains no quartz among its 
porphyritic components. 
