DR. BUNDJIRO KOTO ON SOME JAPANESE ROCKS. 437 
apatite crystals also occur in the augites. Fragments of polysyn- 
thetic felspar, colourless microliths (augites?), and octahedra of 
magnetite occur as microscopic interpositions. 
_ In rare cases, well-developed augite crystals are enclosed by a 
border of opacite aggregations. In the hornblendes of eruptive 
rocks such aggregations are by no means rare, and lithologists are 
in the habit of laying particular stress on this point as being cha- 
racteristic of hornblende in contradistinction to augite when beth 
minerals occur in the same rock. As yet only one such occurrence 
is known to me. 
Pabst * was the first to mention this peculiarity, which he ob- 
served in augite-bearing hornblende-andesite from Kurokami Dake, 
Kiu-Siu. Augite crystals are at times completely bordered by 
augite granules, forming a special zone, which zone, however, causes 
no departure from the original crystallographic outlines. 
The granular wall is affected by the action of polarized light in a 
less degree than the central mass, but the optical orientation is just 
the same, both in the external wall and in the inner augite sub- 
stance. Ddélter and Hussak recently made the experiment of 
smelting dark green augite from a hornblende-andesite from Green- 
wood Furnace, North America. The smelted augite was changed 
into small light-brown grains, the optical characters of which re- 
mained unchanged. Our augites also seem to have undergone a 
partial smelting, and consequently the formation of granules is 
restricted to the periphery. 
The individual crystals are, in general, strongly developed in the 
clinoaxial direction, a,and the glass-enclosures interposed in the plane 
parallel to that direction are flat. In the clinopinacoidal section 
the glass-enclosures appear rounded or oval, with air-bubbles ; few, 
however, attain a moderately large size (0°03 millim.). When 
viewed from the orthopinacoidal face under low powers, the glass- 
enclosures appear as black rods. By employing high powers, and 
especially by moving the micrometer-screw, the black rods are seen 
to be really transparent, and they represent the side view of the 
flat glass-enclosures which are arranged parallel to the clinopinacoid. 
Lamellar structure, so common in the basaltic augite, appears to be 
absent in these crystals. The larger augite crystals are grouped 
together in the most varied manner, sometimes in stellate forms, at 
others two individuals form cross twins, which intersect at an angle 
of 79°. Perhaps this may be the twin whose composition-face is 
the hemidome — P o (Naumann-Zirkel, ‘ Mineralogie,’ 11te Auflage, 
p- 604). These twins can be best studied in the augite of the 
augite-andesite from the Miogi-San, Kozuke province. 
An analysis of the pleochroic augite from Ihama in Izu, the 
material of which was isolated by Thoulet’s solution, gave the 
following results :— 
* Untersuchungen von chinesischen und japanischen zur Porzellanfabrikation 
verwandten Gesteinvorkommnissen.’ Inaug. Dissert. Leipzig, 1880. Also in 
Zeitschr. d. d. geol. Ges. xxxiii. 1880, p. 258. 
