236 JOSEPH P. IDDINGS AND EDWARD W. MORLEY 



biotite, ranging downward to microscopic crystals, also pheno- 

 crysts of augite, but none of leucite or feldspar. In thin section 

 there are abundant small phenocrysts of zonal pleochroic augite, 

 considerable brown mica, zonal lime-soda feldspar, and magnetite, 

 with relatively large crystals of colorless apatite, and a few anhedral, 

 brownish-green hornblendes. There is some ill-defined colorless 

 mineral which may be in part orthoclase, in part leucite. No 

 olivine is to be seen. The chemical composition is very similar 

 to that of No. 3. The norm shows it to be slightly more femic, 

 with more normative nephelite and olivine, and the same amount 

 of normative orthoclase, but the crystallization of abundant 

 biotite accounts for the non-appearance of olivine, and the small 

 amount of leucite without nephelite in the mode. The rock might 

 be classed as a variety of biotite vicoite. 



The rock of analysis No. 6 is dark gray and dense, from Kali 

 Gillinan. It is minophyric, sempatic, with comparatively few 

 large phenocrysts of leucite, and abundant small phenocrysts of 

 augite and leucite. In thin section there are abundant leucites, 

 as phenocrysts, as clusters of crystals, and as microscopic crystals 

 in the groundmass. Some clusters of leucites surround augite, 

 others inclose plagioclase, augite, and magnetite. The phenocrysts 

 of augite have pronounced zonal structure; there is a small amount 

 of euhedral olivine. Small crystals of magnetite in some instances 

 have very irregular outlines owing to pockets of groundmass and 

 partly inclosed minute crystals of augite and plagioclase; the out- 

 line of the magnetite being rounded in places, as is the case with 

 quartzes having similar partial inclusions. The rounded forms are 

 clearly forms of growth and not of solution, as sometimes suggested. 

 The holocrystalline groundmass contains considerable zonal calcic 

 plagioclase, besides minute crystals of the other mineral constitu- 

 ents of the rock. The chemical analysis and norm show that this 

 variety is more femic than the preceding ones, and that it is richer 

 in normative anorthite. Normative orthoclase and nephelite are 

 represented by modal leucite and by albite in the lime-soda feldspar. 

 Olivine is modal as well as normative. The rock may be called 

 a leucitophyre or leucite basanite. 



The rock of analysis No. 7 is gray, dense, and aphanitic with 

 numerous pores, and is found in Kah Sekatak. It has abundant 



