997 



usually with lumierotis plieiionisis df [)l;ii>'ioL*l;isc, sometimes besides 

 green augite also hjpei'sthene occurring among the phenocrists. 



The homoeogeneous inclusions have l)een gathered in porous frag- 

 ments along the slope above the hot spi-ings of Tjipanas, near the 

 brink of the crater. The} are chietly rather fine-granular olivine 

 gabbroes, which bv their pale colour distinctly contrast with the 

 dark lava. The percentage of olivine varies, but is usually rather 

 high. Some of the inclusions consist of basic [)lagioclase, green augite, 

 olivine and magnetite; the olivine crystals with more or less rounded 

 edges are often entirely surrounded by the augites, the latter being 

 angularly bounded with respect to tlie i)lagioclases. Hypersthene being 

 among the constituents there arise graduations into particular inclu- 

 sions in which augite is absent among the constituent minerals, a 

 strong brownish-black to brownish-yellow pleochroitic amphibole 

 and hypersthene both occurring in its place. In these inclusions also, 

 the plagioclase is rather well idiomorphically developed with respect 

 to amphibole and hypersthene, whereas olivine-crystals with rounded 

 edges and sometimes irregularly shaped are entirely enclosed by 

 amphibole and hypersthene. All these rocks represent shapes of 

 different depths of oli vine-basalts, the amphibole seems to be absent 

 in the effusive aecjui\ alents and was either not produced, the circum- 

 stances of crystallization being different, or it was wholly resorbed 

 after crystallization. On the contrary, the rounded shape of the olivine- 

 crystals with their spread framing by amphibole, indicates a resorp- 

 tion of the first-mentioned mineral in the holocrystalline rocks. The 

 inclusions without augite show a rare combination of minerals by 

 the absence of monoclinic pyroxene and the presence of olivine, this 

 mineral generally being absent in am[)hibole gabbroes and similar rocks. 



Olivine-free inclusions are the aequivalents of more andesitic rocks, 

 which we know from othei' parts of the (ioentoer complex. In a similar 

 inclusion there were recognized : plagioclase, both hypersthene and 

 augite, and magnetite. As a rule the plagioclases form the bigger 

 individuals not limited idiomorphically, which in a very large number 

 poikilitically surround small pyroxene crystals. 



Krahitaii . 



During a visit to Krakatau in ilie beginning of May 1913, in 

 one of the basaltic windings west of the great winding of hyper- 

 sthene andesite') angular fragments were collected of a light-coloured 

 fine- to coarser-granular rock, which microscopically examined turned 



Ï) R. D. M. Verbeek, Krakatau, II, p. 160. Batavia 1885 



