THE PETROGRAPHY OF JAVA AND CELEBES 243 



Scattered through the whole are anhedral, interstitial crystals of 

 isotropic mineral, probably sodalite. These are small amounts of 

 pale-green augite, brown biotite, and magnetite. The rock is 

 sodalite trachyte, or sodalite bostonite, approaching phonolite 

 in composition. Its chemical composition is shown in analysis 

 No. 12 and corresponds to a variety of pulaskose, I. 5 (6). (i) 2. 3 (4). 

 The norm contains 1 1 per cent of nephelite and 8 of anorthite, but 

 no lime-soda feldspar is recognizable in thin section. Other 

 varieties of aphanitic, more or less porphyritic, trachytes occur on 

 the north slope of the mountain east of the stream Gentungen, 

 some of which contain small amounts of sodalite; others carry 

 considerable biotite. 



At the west base of the Pic de Maros there is a sheet of surface 

 lava which is exposed at the Falls of Maros, or Bantinoeran, and 

 also along the road farther south, about 3 miles east of Patinoean, 

 where it is columnar, and is overlaid by limestone. The rock is 

 coarsely porphyritic with abundant phenocrysts of black euhedral 

 augite, the largest 7 mm. in diameter, and less numerous dark- 

 brown glassy olivines, in a dark-gray aphanitic groundmass 

 speckled with small white spots. In thin section the augite 

 phenocrysts are brownish green, slightly pleochroic, and zonal, the 

 central part being lighter colored than the margin. Olivine is 

 abundant and there is much lime-soda feldspar in small pheno- 

 crysts, short prismoid and tabular; besides some prismoid ortho- 

 clase and zones of orthoclase surrounding plagioclase. There is 

 a fine-grained matrix of the same kinds of minerals with magnetite 

 and zeolitized feldspathoid mineral which may have been analcite, 

 nephelite, or leucite. The rock is a variety of orthoclase basalt, or 

 absarokite, whose chemical composition is shown by analysis 

 No. 18, III. 5. (3) 4.3, a somewhat more calcic rock than kental- 

 lenose, which is III. 5. 3. 3. 



A comparison of the analyses of rocks from Mt. Mouriah and 

 the Pic de Maros shows that the leucitic rocks of the one and the 

 shonkinitic rocks of the other locality are chemically similar. 

 They are low in silica, high in potash, and relatively high in alumina 

 and calcium oxide. This shows itself mineralogically in the promi- 

 nence of leucite in the lavas of Mt. Mouriah, and of orthoclase and 



