
 ParrIl.§ vi] CRYSTALLINE ROCKS—MASSIVE. 187 
rocks. They were poured out on a great scale during Permian and 
early Triassic times in Westphalia and the Thuringer Wald. 
_ Liparite—(Rhyolite, Quartz-trachyte), a rock composed of a 
compact or fine-grained ground-mass containing crystals of sanidine 
and quartz, often with black mica and hornblende, triclinic felspar, 
augite, apatite, and magnetite. Considerable diversity exists in the 
texture of this rock. Some varieties are coarse and granitoid 
in character. Intermediate varieties may be obtained like the 
quartz-porphyries, passing by degrees into more or less distinctly 
vitreous rocks. Throughout these gradations, however, which may 
represent different stages in the crystallization of an original 
molten glass, a characteristic ground-mass can be seen under the 
microscope having a glassy, enamel-like, porcellanous, microfelsitic, or 
sometimes even a finely granitic character. Ananalysis by Vom Rath 
of a rhyolite from the Kuganean Hills gave—silica, 76°03; alumina, 
13°32 ; soda, 5°29; potash, 3°83; protoxide of iron, 1°74; magnesia, 
0°30; lime, 0°85; loss, 0°32; total, 101°68,—specific gravity, 2°553. 
Liparite is an acid rock of volcanic origin, and late geological 
date which in more recent times has played a part similar to that of 
the granitic and felsitic rocks of older periods, though it has not been 
yet observed as a product of any still active volcano, It forms 
enormous masses in the heart of extinct volcanic districts in 
Kurope (Hungary, Huganean Hills, Iceland, Lipari) and in North. 
America (Wyoming, Utah, Idaho, Oregon, California).* 
Among the rocks above enumerated a distinct gradation can 
sometimes be traced from a thoroughly crystalline granitoid structure 
into a porphyritic mass with the characteristic ground-mass. Among 
the porphyritic varieties also traces can be detected of a vitreous — 
base indicative of the rocks having once existed as glass. The 
vitreous compounds are placed together at the end of the non- 
quartziferous group (pp. 140-142). 
B. Quartaless, or poor in Quartz. 
In this group free quartz is not found as a marked constituent, 
although occasionally it occurs in some quantity, as microscopic 
examination has shown in the case even of some rocks where the 
mineral was formerly believed to be absent. A range of structure 
is displayed similar to that of the quartziferous series. The 
thoroughly crystalline varieties are typified by syenite, which 
represents the granites of the quartziferous rocks, those which 
possess a porphyritic ground-mass by orthoclase porphyry and 
trachyte, answering to quartz-porphyry and liparite. 
Syenite.—This name, formerly given in England to a granite 
with hornblende replacing mica, is now restricted to a rock consist- 
ing essentially of a crystalline-granular mixture of orthoclase and 
1 On liparite or rhyolite see Zirkel, Micro. Petrog. p. 163. King, Explor. 40th 
Parallel, p. 606. 
