CHINA, MONGOLIA, AND JAPAN. 37 



Hiangshui (pu), and also in the coal field of Kiming, where they occur apparently 

 as members of the coal-bearing series, and at a higher level than the lower coal 

 seams. 



The fragments of porphyry that form the characteristic feature of this deposit, 

 have a base that varies in texture, from compact to finely crystalline, in color from 

 dark reddish-brown to black, and that effervesces slightly in dilute muriatic acid. 

 It contains numerous thin, oblong crystals, of a white triclinic feldspar, from one- 

 eighth to three-quarters of an inch long. Through the base are scattered grains 

 of a white mineral, apparently a zeolite, and scales of what seems to be ichthy- 

 ophthalmite. 



In places, these fragments make up the greater part of the deposit, and it is then 

 difficult to distinguish the inclosed from the inclosing rock. In other places the 

 blocks are scattered through a finely crystalline, dark reddish-brown rock, that is 

 irregularly impregnated with a carbonate, and about as hard as compact limestone. 

 It contains also pieces of an amygdaloidal rock, the cells of which are filled with 

 calcite and a white zeolite ; blocks of limestone are also found in it. 



The general appearance and manner of occurrence of this deposit suggests the 

 idea that it is of pluto-neptunian origin, and perhaps contemporaneous with the 

 eruption of the greenstone-porphyry. I will add that I did not meet with dykes 

 of this porphyry. 



Kalgan Trachytic Porphyry. — This rock, and its pluto-neptunian deposits form 

 the hills around Kalgan, and those that, extending S. E. from that city, send out a 

 spur to the west crossing the road from Siuenhwa. 



The porphyry in question is very variable in color, the most common variety 

 being brown, but all shades occur from pitch-black to white, red, and green. The 

 texture of the rock is compact, often almost vitreous, but in structure it ranges from 

 the solid rock of the Kalgan mountain to the cellular and often almost pumiceous 

 variety of the spur between Kalgan and Siuenhwa. 



Crystals of white, transparent orthoclase, or glassy feldspar, are always present, 

 and are generally so limpid as to take the color of the variety in Avhich they are 

 imbedded. Small grains of pellucid quartz occur more rarely, but seem in places 

 to belong to the primary ingredients, though they are generally secondary. Mica 

 and hornblende are always absent. 



The cells are sometimes long-cylindrical, but more generally -flattened, though 

 lying in the same direction. They are filled with different varieties of quartz, as 

 cornelian, chalcedony, and a black silex. More rarely they are filled with calcite. 



The base of this rock fuses easily before the blowpipe to a white vesicular glgiss 

 on the edges. 



In intimate connection with this porphyry are strata of a deposit which, from 

 their character and manner of occurrence, appear to be of pluto-neptunian origin, 

 and were probably formed contemporaneously with the eruption of the porphyry. 

 These consist chiefly of a tufa, varying in color from white and gray to purple, and 

 in hardness between that of chalk and limestone. Its texture is rough and earthen 

 in appearance. Through the mass are scattered crystals of glassy feldspar, grains 

 of limpid quartz, and hexagonal scales of dark-brown mica. 



