S. Powers — Notes on Hawaiian Petrology. 275 



were possibly connected with the same volcanic activity. 

 Puu Palailai, the lowest of the Laeloa craters of West 

 Oahu, is at a slightly higher elevation than any coral lime- 

 stone in the vicinity and no contact of the lava with the 

 limestone is exposed. Therefore the age of these craters 

 is undetermined. 



Olivine nodules.— Along the line of a new ditch from the 

 western portion of the Lihue district to Koloa, Kauai, 

 about one mile northeast of Puu Kahoaea, a basalt filled 

 with masses of olivine has been excavated. The olivine 

 nodules vary in size, the largest being 6 to 8 inches in 

 diameter. They are rounded or subangular in outline 

 and of a uniform composition throughout. In most cases 

 they are smooth and rounded on the outside and they can 

 be broken from the matrix. Vesicles frequently occur 

 clustered around the inclusions, but they are not found 

 elsewhere in the rock. The matrix is a fine-grained pic- 

 ritic basalt or limburgite of dark grey color. Olivine 

 phenocrysts are present and the groundmass is composed 

 of augite, olivine, iron ores, and abundant glass with a 

 very small amount of plagioclase feldspar. The inclu- 

 sions are a dunite composed principally of olivine with a 

 very subordinate amount of diallage and very rare specks 

 of iron oxide. 



The striking features of the nodules are large size and 

 abundance. They compose about half the volume of the 

 rock. They are usually very fresh and the individual 

 olivine crystals are frequently a quarter of an inch in 

 length. 



On account of the deep weathering which the region 

 has undergone, it is impossible to determine whether the 

 nodule-bearing rock is part of a dike or a flow, but it is 

 probably a flow, since the nodule-bearing rooks have a 

 rather wide lateral distribution. The inclusions are found 

 northward to the Peohia stream. Smaller nodules occur 

 in the basalts near both ends of the new tunnel between 

 the Komooloa and Palikea streams and a few are found 

 in the Waiahi and Iliiliula stream beds. Similar nodules 

 occur in the Hanapepe River, especially in the main 

 stream above the falls 25 and a few are found in the flows 

 on the east side of Nawiliwili Bay. Olivine bombs 

 have been found on Hualalai and on Mauna Kea, 2G and 

 olivine nodules have been reported from Oahu. A 



25 W. Cross, op. cit., p. 13 ; collected by the writer above the falls. 



26 E. A. Daly, Jour. Geol., vol. 19, pp. 301-3, 1911. 



Am. Jour. Sci.— Fourth Series, Vol. L. No. 298.— Octorer, 1920 

 20 



