Classification of Massive Rocks. 301 
(b 2) acmite trachyte, in which the amphiboloids are 
acmite, ægerine and arfvedsonite. 
(c) andesitic trachytes, with a hyalopilitic ground mass 
tending strongly to a glassy development. 
(c 1) biotite-hypersthene-trachyte, containing biotite, 
hypersthene, augite and sanidine in a glassy 
ground mass, 
(c 2) the Arso type, in which sanidine and augite are 
the principal porphyritic minerals, and the 
ground mass is hypocrystalline. 
(D) hyalo-trachyte, consisting principally of glass, with the 
composition of trachyte. 7 
2. QUARTZLESS PANTELLERITES, have anorthoclase and iron- 
earing minerals as porphyritic constituents. 
C. THE PHONOLITES. 
The phonolites embrace the quartz-free combinations of an alka- 
line feldspar with the minerals of the nepheline and leucite groups, 
and usually a monoclinic augite. 
They include :— 
l. PHONOLITES PROPER, containing nepheline and feldspar as the 
essential porphyritic constituents, as well as the 
essential components of the ground mass, which is 
-holocrystalline, hypocrystalline, or glassy. 
(A) trachyte-phonolite, in which sanidine predominates over 
the nepheline, particularly in the ground mass. 
(B) nephelinite-phonolite, in which nepheline predominates 
over the feldspar. , 
(c) hyalo-phonolite or Phonolite Glass, a glass with the 
composition of phonolite, containing microlites of 
sanidine and augite. 
2. LEUCITE-PHONOLTTES, containing leucite instead of nepheline — 
among the porphyritic constituents. E 
3. LEUCITOPHYRES, containing both leucite and nepheline in addi- 
tion to sanidine. 
D, THE DACITES. 
The dacites are quartz-bearing plagioclase rocks. They contain, 
also, one of the iron-bearing minerals of the biotite, amphibole or 
Pyroxene groups. Rea ee 
