122 



U. S. Washington — Basalts of Kula. 



grains, with some trichites. Phenocrysts, of hornblende, 

 augite and olivine, are abundant, the first being generally 

 altered to the " brown aggregate " stage. Those of a " semi- 

 vitreons" structure have a pitchy luster. In them the ground- 

 mass shows a largely preponderating quantity of clear cinna- 

 mon brown glass, and they have lost, with reduced number of 

 microlites, the hyalopilitic structure of the preceding. Some 

 greenish hornblende appears, but this, as well as the brown, is 

 commonly free from alteration, and the alteration when present 

 is always to "brown aggregate." The tachylytes are very 

 compact, jet black, with a vitreous luster, many specimens 

 looking like anthracite. They consist almost wholly of a clear 

 dark chocolate brown glass, often streaked. Very few micro- 

 lites and no magnetite are present. Phenocrysts are repre- 

 sented by large augites and hornblende crystals, the latter 

 frequently showing a zonal structure, but always fresh and 

 unaltered, both brown and green, the latter having become 

 more frequent. Olivine is very rare. The average sp. gr, of 

 the hyalopilitic type was found to be 2-655, of the semi-vitreous 

 2-704, and of the tachylytes 2-721. Two lava streams of Kula 

 Devlit are leucitic. They are both hyalopilitic in structure, 

 and, apart from the presence of leucite in not very abundant, 

 small crystals, are not markedly different from the non-leueitic 

 type. Their sp. gr. is 2'7l9. 



The following may be selected as typical analyses out of 

 those made for me by Dr. A. Rohrig of Leipzig. 



H 9 0(lgn.)~- 

 SiO 



A. 

 002 



. . 48-24 



B. 



0-46 

 47-50 

 19-32 

 4-75 

 5-20 

 8-37 

 4-36 

 7-63 

 2-31 

 0-21 



C. 



0-04 

 47-74 



A1„0 3 



Fe"0 



... 20-64 

 -_. 4-63 



20-95 

 3-29 



FeO 



CaO 



MgO 



Na„0 



KO.. 



5-55 

 7-94 

 5-02 



5-0S 

 T88 



6-32 

 7-56 

 5-16 

 7-12 

 1-21 



p;o 5 



.. 0-97 



0-13 







. 





99-97 100-11 99-52 



A = Second period Kulaite from well-digging in Kula. Sp. gr. = 



2-733. 

 B = Third period. Early stream of Kula Devlit. Sp. gr. = 2-704. 

 C = Third period. North stream of Kula Devlit. Leucitic. 



Sp. gr. = 2 736. 



The mutual similarity is most marked, but nothing special 

 need here be said, except to call attention to the small quantity 

 of K 2 in the leucitic specimen, analysis C. 



