370 RESEARCH IN CHINA. 
teristic forms. Ilmenite is frequently surrounded by narrow fringes of 
titanite and the latter is also distributed in unusual profusion throughout 
the rock in the form of irregular grains. Pyrite grains included in hema- 
tite pseudomorphs are also not uncommon. 
Other accessories, such as apatite, rutile, and greenish tourmaline, 
occur rather abundantly in very small crystals. A few of the epidotes 
also inclose allanite. 
Gray biotite gneiss, No. 22.—This is one of the common types of gray 
gneiss in Shan-tung. Specimen collected near the village of Ch’ang-hia, 
associated with No. 21. 
This is a rather dull-gray gneiss of fine texture and blended colors. 
Although the banding is distinct, the lamine are not well defined, and 
the individual layers can not be traced for any considerable distance. 
In this phase of the gneiss there is no development of the “‘augen.”’ 
The predominant minerals disclosed by the microscope are quartz, 
orthoclase, and biotite. With these are associated, in subordinate quantity, 
plagioclase, magnetite, titanite, apatite, epidote, rutile, and zircon. The 
larger quartz crystals show undulatory extinction strongly, and are some- 
what granulated along their edges in certain places. The orthoclase shows 
similar features and, in addition, is frequently crossed by zigzag fractures. 
This feldspar is also partly changed to brown decomposition products, 
particularly along the principal cleavage planes and near the centers of 
the crystals. The plagioclase always extinguishes at low angles, indicating 
that it is probably albite or oligoclase. It has suffered less alteration than 
the potassic feldspar. 
The greenish plates of biotite are arranged in roughly parallel seams. 
They are not much altered, but wherever they are decayed epidote is pro- 
duced through the well-known reaction which is common in the belt of 
weathering.* 
Fine-grained epidote gneiss, No. 34.—A rather unusual phase of the 
T’ai-shan gneisses. Collected near the great stairway on the T’ai-shan, 
at an elevation of 4,500 feet, 1,350 meters, above sea-level. 
The gneiss is light-gray with a tinge of green, and in spite of the very 
fine texture, the arrangement of the darker and lighter minerals in bands 
is quite distinct. The quartz and feldspars are almost colorless, the green- 
ish hue being due to the presence of epidote and hornblende. 
Quartz, orthoclase, and epidote are the dominant minerals. A sodic 
feldspar, zoisite, biotite, and hornblende are less abundant; and there 
is a scattering representation of the usual accessory minerals, such as tita- 
nite, hematite and magnetite, zircon and apatite. 
* Van Hise: A Treatise on Metamorphism, p. 340. 
