PLATE LIV. 
STRAIN PHENOMENA IN FELDSPARS. 
A. Microcline and vein-structure in feldspar. The minerals of the slide are chiefly quartz 
and feldspar. Near the center a quadratic crystal of orthoclase exhibits microcline 
grating on the lower side and a set of gash-veins on the upper. Both are regarded as 
effects of distortion of the rock during metamorphism. (Biotitic granite from the Arch- 
ean complex inthe T’ai-shan, Shan-tung. Specimen 33, crossed nicols, x 52, page 374-) 
B. Gash-veins in feldspar. Most of the field is occupied by a large crystal of orthoclase 
which incloses a slightly decayed body of orthoclase. Locally microcline grating 
may be observed in the orthoclase—the areas which possess this structure having no 
definite boundaries. The wavy white streaks are vein-like bodies of a sodic feldspar 
which appears to fill cracks in the orthoclase. Along the right-hand edge of the 
crystal these veins may be seen to coalesce with the white albite cement which has 
developed in consequence of the granulation and recrystallization of a portion of 
the rock. (Red gneissoid granite from the Archean complex in the T’ai-shan, Shan- 
tung. Specimen 32, crossed nicols, x 40, page 372.) 
C. Gash-vein structure in feldspar. A large orthoclase crystal crossed by two intersecting 
sets of gash-veins which are filled with a feldspar of slightly different optical properties. 
The veins are believed to be the filling of cracks developed by torsional strains in the 
feldspar. (Dark biotite-granite from the Archean complex in the T’ai-shan, Shan- 
tung. Specimen 31, crossed nicols, X 55, page 375.) 
LIMESTONES FROM SHAN-TUNG. 
D. Conglomeratic limestone, showing the end of one of the pebbles highly magnified. 
The dark pebble on the left is minutely crystalline and contains abundant ferruginous 
impurities. The matrix on the right is clear crystalline calcite. The normal margin 
of the pebble represents the smoothly worn original surface; the edge seen in this 
slide has been corroded and is indented by calcite crystals of the ground-mass. 
(Conglomeratic limestone from the Upper Cambrian near Yen-chuang, Shan-tung. 
Specimen 47, ordinary light, x go, page 384.) 
E. Shell nucleus in red oolite. The dark oolitic bodies show the concentric structure 
typical of such rocks. The nucleus of the largest body is a bit of shell of some 
invertebrate. The matrix of the rock is clear granular calcite and the fractures which 
traverse the slide are filled with the same mineral. (Red oolite from the Man-t’o 
formation near Ch’ang-hia, Shan-tung. Specimen 14, ordinary light, x 20, page 378.) 
F. An oolitic body containing a fragment of an older body of the same character. In 
both nucleus and enveloping crust, the concentric and radiate structures are clearly 
visible. The dark streaks are amorphous hematite. It will be noted that the radiate 
structure is more prominent on the convex than on the flat side of the nodule, suggest- 
ing that the structure may be due to radial cracks produced by expansion from 
within. (Red oolite from Ch’ang-hia, Shan-tung. Specimen 10, ordinary light, 
X 50, page 379-) 
