460 E. S. Dana — Petrography of the Sandwich Islands. 



grains, though also in indistinct crystals and occasional rod-like 

 forms. These often contain abundant glass inclusions. The 

 grains are often packed about with a poorly defined border of 

 augite and it is in this zone particularly that the little rods of 

 titanic iron are regularly orientated, standing out from the 

 chrysolite in the manner already described. Besides this, it is a 

 granular mixture of augite and plagioclase not showing any 



flass. The other specimen (15), from the foot of Waldron's 

 ,edge, is a light-gray cellular rock, highly crystalline, the 

 minute cavities lined by plates of feldspar and tables of titanic 

 iron. It is much like some of the specimens described from 

 Mauna Loa (p. 448), and with them is characterized by the 

 same milk-white spherical mineral in the cavities, provisionally 

 referred to phacolite. 



The lavas from the west wall of Kilauea west of Halemau- 

 mau are all closely similar in character among themselves : they 

 are dark-gray in color, vesicular, and contain a fair amount of 

 chrysolite. The structure is throughout crystalline, rather 

 coarsely granular, and the chrysolite is marked by its usual 

 bristling border of titanic iron. One or two of these show 

 something of the radiating augite forms. 



3. Ejected masses on the border of Kilauea. — The specimens 

 from the borders of Kilauea are supposed to have been ejected 

 at an explosive eruption about a century since. The larger 

 part of the masses are described by Professor J. D. Dana as 

 being of a fine-grained, gray, slightly vesicular lava. Other 

 specimens* are reddish or chocolate-colored, coarsely granular 

 and highly crystalline. In the latter, the chrysolite is present 

 in very large amount and has suffered from alteration, probably 

 by the action of heated water vapors, so that the fractured 

 surface is either dull-red and opaque or else slightly iridescent. 

 The feldspar crystals are clear and glassy, and where there are 

 cavities they often project in distinct transparent plates from 

 the walls. The crystals have an angle of extinction of —14° 

 with the blc edge, and hence conform to labradorite, like 

 those of similar occurrence among the Mauna Loa specimens. 

 Under the microscope the chrysolite is seen to be surrounded 

 with a deep-red border, and the iron oxidation has penetrated 

 into the mass of the crystal sometimes along broad fracture-lines, 

 and more generally in a network of fine wavy lines giving it a 

 peculiar feathery aspect. Not infrequently the oxidation has 

 gone so far that the chrysolite is perfectly opaque and by reflec- 

 ted light is bright brick-red. 



Specimens 6, 7, 9f are examples of the light-gray lavas but of 

 peculiar characters. No. 9 is a light-gray rock conspicuous 

 among all those under examination for its beautiful crystalline 



* Here belong Xos. 3, 8 with G.=3-18, 10 with G.=3"15. 

 f For 6, G. = 3-15; for 9, G. = 3"10. 



