TRACHYTE ON THE ISLAND OF HAWAII 



515 



LIST OF ROCKS IN TABLE OF ANALYSES. 



Rock 



1 . Trachyte obsidian 



2. Trachyte 



3. Glaucophane-solvsbergite 



4. Hornblende-sol vsbergite. . 



5. Hedrumite 



6. Foyaite 



7. Litchfieldite 



8. Pulaskite 



9. Phonolite 



ID. Quartz-syenite-porphyry . 



11. Eiotite-trachyte 



12. Lestiwarite 



13. Nordmarkite 



14. Bostonite 



15. Pyroxene-syenite 



16. Riebeckite trachyte 



Locality 



Puu Waawaa, Hawaii 



Puu Anahulu, Hawaii 



Cape Ann, Massachusetts. . . 



Laugendal, Norway 



Osto, Norway 



Gran, Norway 



litchfield, Maine ■ 



Salem Neck, Massachusetts.. 

 Devil's Tower, South Dakota 

 Bearpaw Mountains, Mon- 

 tana 



Yellowstone Park, Wyoming 



Laugendal, Norway 



Tonsenas, Norway 



Laugendal, Norway 



Kunsamo, Finland 



Berkum, Germany 



Analyst 



W. F. Hillebrand 

 W. F. Hillebrand 

 H. S. Washington 

 L. Schmeick 

 V. Schmeick 

 L. Schmeick 

 L. G. Eakins 

 H. S. Washington 

 L. V. Pirsson 



H. N. Stokes 

 W. F. Hillebrand 

 V. Schmeick 

 G. Forsberg 

 V. Schmeick 

 N. Sahlbom 

 H. Laspeyres 



the feldspars and much less abundantly in minute stout prisms. 

 The two most distinct minerals are respectively colorless and clear pale 

 yellow, of strong refraction and double refraction, approximately like 

 diopside or acmite. Extinction is parallel for the colorless prisms and 

 never more than 10° for the yellow ones. There is no visible pleo- 

 chroism in either, hence lovenite seems to be excluded. The norm 

 of the glassy rock shows the acmite molecule, but no recognizable 

 acmite, aegirite, or riebeckite has been noticed. As the analysis 

 shows zirconia and titanic acid in determinable quantities, it is 

 possible that rare or unknown zirco- or titano-silicates are present. 

 Clear glass and dark globulitic areas are present in small amount. 



A glance at this trachytic rock suggests its close relationship with 

 the obsidian of Puu Waawaa. It is not sufficiently fresh, as to its 

 dark constitutents, to warrant full analysis, but the feldspars are only 

 slightly attacked, and a partial analysis by Dr. Hillebrand, given in 

 column 2 of the table, demonstrates sufficiently the practical identity 

 of the two rocks. 



The position of the obsidian in the Quantitative Classification of 

 Igneous Rocks'" is shown by the norm calculated from the analysis, 

 which is as follows: 



I Whitman Cross, Joseph P. Iddings, Louis V. Pirsson, and Henry S. Wash- 

 ington, Quantitative Classification of Igneous Rocks, Chicago, 1903. 



