446 DR. BUNDJIRO KOTO ON SOME JAPANESE ROCKS. 
resulting mass is green and fibrous. When decomposition is further 
advanced, the viridite dwindles away and becomes entirely replaced 
by calcite, which then forms pseudomorphs after the augite. As 
augite in becoming viridite increases in volume by taking up water, 
so the dirty green fibrous mass pushes itself into the ground-mass 
everywhere and fills up the clefts in the felspar. Some apatite is 
present. There is no glass-basis. The following is an incomplete 
analysis of this rock :— 
SOs Sacye ee abe 59:14 
FOO. ate 11°85 
Ni Opap vee see 13-64 
CAG a ake ance 8°96 
OA LO Jere ee 3°14 
Specific gravity 2°5764. 
In the rock from Kasiwada the augite is completely decomposed 
and represented by hydrous sesquioxide of iron. Porphyritic augite 
is scarce, but the ground-mass is exceedingly rich in augite grains 
and microliths. The felspar precedes the augite in crystallization. 
This augite-andesite possesses a diabasic character, that is to say, 
the crystallization of the Mg-Fe-silicate has generally taken place 
later than that of the components poor in iron, viz. felspar and its 
vicarious components. This holds good both for the porphyritic 
constituents and for the ground-mass. The interstitial spaces of 
the ground-mass of this rock are filled with a bottle-green devitrified 
substance which is but partially isotropic. The rock is traversed 
by veins and secretions of calespar and chalcedony. The former is 
easily soluble in hydrochloric acid, leaving a skeleton of chalcedony — 
behind in the veins. 
The rocks from the Fusiwara pass* and also from Yawatat are 
exceedingly rich in specular iron. In the latter the plagioclase is 
irregularly broken and indented. Light reddish-brown or grey 
apatite is tolerably abundant. 
The augite-andesite from the Midgi-San in Kozuke has been 
concisely described by R. v. Drasche ¢. J. Rein §, in his work, called 
it a dolerite, and in another place a doleritic lava ||. 
It is a brownish grey coarsely porphyritic rock consisting of 
augite, plagioclase, and magnetite, but no olivine; it is therefore 
not a dolerite, although its structure is doleritic. The augite 
crystals are strongly pleochroic and rich in specular iron. The 
augite forms the cross twins, whose composition-face will be most 
likely —PRo. The felspar shows few polysynthetic lamellations, 
but has a beautifully zoned structure. The ground-mass is 
holocrystalline, being a mixture of lath-shaped felspar crystals and 
augite microliths together with magnetite. The rock from the 
* Tn the province Izu. t Kai. 
t Neues Jahrb. 1879, ii. p. 41. 
§ Petermann’s ‘Geographische Mittheilungen,’ Erganzungs-Heft 7 Der 
Nakasendo, p. 33. 
|| ‘Japan,’ Band i. p. 47. 
