ANDENDIORITE IN JAPAN 823 
Quartz which is surely primary is totally allotriomorphic, and 
fills up the interspaces between feldspar crystals. It is always 
fresh, contains glass enclosures, and sometimes well-shaped 
crystals of pyrite. 
Magnetite is very common. An opaque ore,’perhaps ilmenite, 
undergoes decomposition in such a manner as to leave more 
resisting lamella cutting each other at 60°. The pyrite con- 
tained in quartz is certainly of primary orgin. 
Notwithstanding the holocrystalline structure of the rock, 
there are, occasionally, remnants of groundmass, which consist 
of microscopical grains of plagioclase, hornblende and iron ores. 
In a fine granular, porphyritic variety of the diorite, phenocrysts 
of feldspar are scattered in the aggregate of smaller lath-shaped 
feldspar individuals, which corresponds to the groundmass of the 
neovolcanic rocks. The above mentioned facts seem to show 
that the diorite is not a normal plutonic rock, but most probably 
a sheet or dike, which has solidified in the region of slight 
pressure. 
Contact metamorphism.— In the neighborhood of the diorite, 
the propylite is so highly decomposed that traces of the contact 
metamorphism cannot be recognized. Although the Tertiary 
beds are never found in contact with the diorite dike, a Tertiary 
shale found about 330 feet to the north of the diorite is har- 
dened like a hornstone and contains iron pyrite, which is not 
usual with the unaltered shale of the region. This change of 
shale seems to be due not to the action of the propylite lying 
between the diorite dike and the shale but to the diorite itself, 
which, in fact, has been taken out from a railway tunnel exca- 
vated close to the exposure of the shale. It seems probable 
that similar diorite dikes run through the Tertiary beds every- 
where beneath the surface, because we frequently find hardened 
shale with a contact mineral, whose exact nature has not yet 
been ascertained. 
Steizner * describes a quartz-bearing mica-diorite of Argen- 
tine under the name of ‘‘Andendiorit”’ as a neovolcanic dike 
*STELZNER, Geologie u. Palzontologie von Argentina, p. 213. 
