458 RESEARCH IN CHINA. 
A medium-grained, greenish-black dike-rock of even texture. Prob- 
ably 85 to 99 per cent of this rock is composed of a blue-green hornblende. 
It occurs usually in ragged interlacing bundles or long rods. In some 
places it appears to be fairly compact, being somewhat frayed only at the 
edges. Throughout the rock, even in the areas where quartz and other 
minerals predominate, detached rods of hornblende are abundant. ‘These 
bodies are not separate crystals, but are apparently shreds of larger crys- 
tals such as would be formed if the hornblende were torn apart along the 
two prominent cleavage planes. Although the mineral is relatively fresh, 
there are numerous areas which are blackened by the separation of iron 
ores in minute particles, with or without quartz and calcite. Such altera- 
tions as these are evidently the result of recent weathering. It is highly 
probable that this secondary hornblende has been derived from pyroxene, 
but there remains nothing either of form or substance which can be defi- 
nitely relied upon as a clue in seeking the origin. 
Spaces not occupied by the hornblende are now filled with clear quartz 
inclosing abundant grains of epidote and occasionally other minerals. 
These are doubtless the end-products of the complete alteration of original 
pyroxene and feldspar. The bulk of the material has been constructed 
into hornblende, leaving an excess of quartz and epidote filling the inter- 
stices. In addition to epidote and quartz, these light-colored areas contain 
a few irregular crystals of zoisite and a colorless garnet which is probably 
grossularite. 
The iron ores occur in rather large, irregular bodies. Pyrite is plentiful, 
but ilmenite is the more common variety and is almost invariably bordered 
by titanite. Titanite also occurs in granules, and these granules are some- 
times aggregated into dense clusters of considerable size. The granular 
occurrence of the titanite and its close association with ilmenite suggest 
that it is a secondary product due to alteration of the latter. The altera- 
tion of ilmenite to leucoxene, known to be a finely divided form of titanite, 
can be observed in this slide. The granular titanite could readily be 
produced by the crystallization of the leucoxene. Thus bits of ilmenite 
which were only partially changed would be surrounded by borders of 
titanite; while granular sphene would occupy the places of other fragments 
which had been entirely altered. In this case the iron has not produced 
magnetite, but has been disposed of in some other way.* 
The pyrite occurs in irregular bodies which are sometimes more or less 
completely inclosed in a carbonate which can not be distinguished from 
calcite. 

*For the usual reaction, see Van Hise: A Treatise on Metamorphism, U. S. Geol. Surv. Monograph 
SL Vil aeey. 
