456 DR. BUNDJIRO KOTO ON SOME JAPANESE ROCKS, 
white grains or fibres which blend into one another, constituting a 
micro-felsitic matter. 
DIABASE. 
Hinazuru pass, Kat province. 
This typical diabase is a green finely granular crystalline rock, 
essentially consisting of clinotomous felspar (0-2 millim.), augite, 
ilmenite, and chloritic matter. Under the microscope the plagioclase, 
as is usual in diabase, is partially decomposed and is traversed by 
many oblique cracks, which are filled up with a green chloritic 
matter, while sometimes it is rich in pseudophitic decomposition- 
products. The extinction-direction of the felspar is 25°-35° with 
the twin lamelle. Here and there unstriated sections are found, 
which may represent either a plagioclase-brachypinacoid or an 
orthoclase-clinopinacoid ; but the presence of orthotomous felspar 
could not be made out with certainty. 
Augite is found as an interstitial mass of grains or erystals 
between the felspar crystals. It may therefore have been erystal- 
lized out after the felspar. The rock consequently has the so-called 
chabasic granular structure. No well-developed augites are visible. 
The zigzag outlines of the augite are due to its occurrence between 
the felspar crystals. No trace of pleochroism is discernible. 
Next in importance is the chloritic matter. It is green, yellow, 
brown, and always fibrous. In some portions the fibres are parallel, 
in others confused. Intermixed with the chloritic matter, we find 
many black grains with a grey decomposition-product (leucoxene) ; 
the black grains are most likely ilmenite. Apatite is wanting. 
The following is the analysis of this rock :— 
SIO esas f 50°22 
ALO) Day ects t 19°41 
He Qe Hes ioe 8:15 
CaO, Whe thes ao 18 10°20 
MON Ue tet 714 
Nass eae ee 3°84 
ROO eae o4, 1:20 
loss‘on denthiony |b..4 Pie iL-10 
101°26 
Discussion, 
The PrestpENT, in speaking of the value of the paper, said that 
he had seen crystals of hornblende bordered by augite like those 
described by the author. 
Mr. Tratt remarked on the great value of the paper. The 
author’s observations on the pleochroic pyroxene tended to confirm 
those made by Dr. Oebbeke on some rocks from the Philippine 
Islands. They did not, however, affect the existence of an im- 
