78 STRUCTURAL AND FIELD GEOLOGY 
believed to be true metamorphic rocks, and they frequently are dovetailed 
with or graduate into mica-schist, and even into sedimentary rocks. 
There are certain coarse-grained gneisses, however, which are less 
markedly schistose, but show a rudely parallel banded structure that 
seems comparable to the banded structure seen in some massive 
igneous rocks. Gneisses of this character may therefore be truly eruptive 
rocks. [The term gvezss is frequently applied to any coarsely crystalline 
granitoid schistose rock. ] 
Chlorite-schist is a schistose aggregate of scaly chlorite, 
usually with quartz, and often with felspar, talc, mica, actinolite, 
or magnetite—the last being frequently disseminated as 
perfect octahedra. 
Talc-schist is a green to greenish-grey or yellow schistose 
rock, very soft, and with a pronounced unctuous or soapy feel. 
It consists chiefly of scaly talc, with which quartz and 
chlorite, or mica are often associated. Other minerals may 
be present, such as felspar, actinolite, magnetite, magnesite— 
the last often in large rhombohedrons. /otstone is the name 
given to a massive fine-grained to compact aggregate of talc 
and chlorite. 
Amphibolites are either schistose or massive—their chief 
ingredient being hornblende or actinolite. The texture 
varies from fine-grained or compact to coarsely crystalline. 
Many other minerals may accompany the amphiboles, such 
as felspar, quartz, pyroxene, garnet, epidote, mica, rutile, 
sphene, magnetite, etc. 
fHlornblende-schist, a schistose aggregate of hornblende, usually 
contains some felspar ; quartz, black mica, and other minerals may also 
be present. The rock is dark green to black. Usually the folia are 
thick, but sometimes they are very fine, and the schist then assumes 
almost a slate-like character. When the foliation is indistinct or not 
apparent we have the variety known as Hornblende-rock. Actinolite- 
schist is composed mainly of light or dark green actinolite, with which 
felspar and other minerals may be associated. When the schistose 
structure is obscure or wanting, we have Actinolite-rock. Some of the 
dark fine-grained amphibolites are hardly to be distinguished in hand- 
specimens from ioe ont 
Granulite.*—A finely schistose halosoyete ts aggregate ‘of felspar 
* There is unfortunately some confusion as to the use of the term 
gvanulite, Some French geologists restrict the term to a fine-grained 
granite in which the mica and sometimes the quartz are hardly recognis- 
able by the unassisted eye—so that the rock seems to consist almost 
) 
