S. Powers — Notes on Hawaiian Petrology 1 . 261 



East of the house fine-grained basalt of light grey color 

 was collected. Microscopically the rock is uniform in 

 grain and slightly glassy in composition, with ophitic and 

 diabasic angites between feldspar laths. Magnetite is 

 quite abundant in shreddy aggregates growing around 

 the other crystals and sometimes included in them. 

 Olivine crystals with limonite rims are present. 



Pebbles of fine-grained, grey basalt were collected on 

 the beach. They resemble in color a rock described to 

 the writer as occurring on the southwest side of the 



156° 37' 



KAHOOLAWE 



20*33' 



Fig. 2. Map of Kahoolawe, Hawaiian Islands, showing cones and craters. 

 (Topography, U. S. Coast and Geodetic Survey.) 



island. One specimen in this section is seen to be an 

 altered tuff 6 with fragments of glass and calcic plagioclase 

 accompanied by grains and granular aggregates of some 

 other material imbedded in a very fine cryptocrystalline 

 groundmass. The other material for the most part ap- 

 pears to be melilite, with a moderately high mean refrac- 

 tion, very low double refraction, parallel extinction on 

 poor cleavage, and shows alteration products that look 

 like zeolites. Some other material of higher double re- 

 fraction may be pyroxene. The other specimen of grey 



6 The writer is indebted to Professor Charles H. Warren, of the Massa- 

 chusetts Institute of Technology, for this microscopic description. 



