210 Classification of Massive Rocks. 
They are divided into three divisions, as follows :— 
1. TRUE GRANITES, containing both light- (muscovite) and dark- 
colored micas (biotite, etc.), including 
(A) lithionite granite, in which the dark ingredient is a 
lithium mica. 
(B) luxullianite, in which tourmaline replaces the lithio- 
nite. 
2. GRANITITES, containing a biotite as its only micaceous constit- 
uent, including 
(A) lithionite granitite, with a lithium mica as the promi- 
nent micaceous constituent. 
(B) amphibole granitite, containing an amphibole in addi- 
tion to biotite. 
(c) augite granitite, in which an augitic mineral is present. 
3. AMPHIBOLE GRANITES, containing amphibole in place of the 
biotite of the granitites. | 
B. THE SYENITES. 
Syenite differs from granite in the entire or almost entire absence 
of quartz as an essential constituent. The syenites besides contain 
no primary muscovite, but do contain a greater or less amount of 
plagioclase. The alkaline feldspars embrace, in addition to ortho- 
clase, both albite and anorthoclase to a subordinate degree. 
They are divided into :— 
1. TRUE SYENITEs, or hornblende syenites, composed of orthoclase, 
hornblende, and usually a little biotite. 
2. Mica SYENITES, which often contain albite in addition to ortho- 
clase and biotite. 
3. AUGITE SYENITES, in which a monoclinic augite and orthoclase 
constitute the essential components. 
C. THE ELÆOLITE SYENITES. 
The elæolite syenites are quartz-free combinations of orthoclase 
and elæolite with one or more of the iron-bearing minerals of the 
pyroxene, amphibole or mica groups. With these is almost always 
associated some plagioclase and a greater or less amount of sodalite. 
Their structure, though usually granular, sometimes becomes 
porphyritic through the occurrence of feldspar, elæolite and soda- 
lite in two generations. It is probable that this structure is con- 
