PLATE LVII. 
AMPHIBOLITES IN THE WU-T’AI SYSTEM. 
A. Caleareous amphibolite. The upper portion of the field consists of matted fibers of 
actinolite. The lighter part below shows quartz, feldspar, andcalcite. Nearthe middle 
of the figure large biotite flakes have developed since the formation of the actinolite 
and have absorbed needles of the latter without disturbing their parallel arrangement. 
(Near the base of the Shi-tsui series, 4 miles south of Shi-tsui, Shan-si. Specimen 
85, slide (6), polarized light, x 25, page 430.) 
B. Gneissic amphibolite. The light-colored field is a mosaic of quartz and feldspar. 
Little dark flakes of biotite mark the horizontal trend of the gneissic bands. A large 
porphyritic crystal of hornblende on the right includes portions of the banded ground- 
mass in which it has grown. (A member of the Shi-tsui series, 3 miles northwest 
of Shi-tsui. Specimen go, slide (6), polarized light, x 20, page 431.) 
ROCKS OF THE HAN SYSTEM. 
C. Gneissic graywacke, showing unreduced bodies of feldspar in eye-spots surrounded 
by the schistose matrix of the rock. The light streaks are quartz and feldspar, and 
the dark areas chiefly biotite. (Schists near Pa-kua-miau, Shen-si, probably of the 
K’ui-chéu formation. Specimen 132, slide (6), polarized light, x 27, page 445.) 
D. Soft greenish slate. Section is transverse to the cleavage and shows numerous unre- 
duced grains of quartz deformed into lenticular bodies. Some of them have been 
sliced diagonally in the process of deformation. (Paleozoic slates, probably represent- 
ing the Sin-t’an formation, at Han-wang-ch’6ng, Shen-si. Specimen 128, slide (6), 
polarized light, x 50, page 449.) 
E. Crumpled black slate. The finely crystalline mass of quartz and graphitic matter 
has been intensely contorted, as shown by the wavy black streaks. In some cases the 
folds pass over into microscopic overthrusts. (Coal-bearing slates of the Wu-shan 
formation at Siau-tau-ho, Shen-si. Specimen 131, slide (a), ordinary light, x 17, 
page 447.) 
F. Mica-schist. Large ragged flakes of biotite inclosed in a schistose mass of quartz, 
feldspar, and muscovite. The biotites are younger than the schistosity and occlude 
portions of the mica streaks which they have absorbed during their growth. (Late 
Paleozoic schists, Shi-ts’tian-hién, Shen-si. Specimen 115, slide (6), polarized light, 
x 45, page 453.) 
