F. L. Ransome — Lava Flows of California. 371 



The ciminites are " characterized mineral ogically by the 

 presence of orthoclase, with basic plagioclase, augite or diop- 

 side, and olivine."* 



The andesite from Carbezo Felipe contains phenocrysts of 

 feldspar and biotite. Sanidine occurs in crystals over a centi- 

 meter in length, but the main bulk of the feldspar is labra- 

 •dorite and andesine. Both monoclinic and orthorhombic 

 pyroxene are present, and the rock is rich in zircon and apatite. 



Concerning the classificatory position of this rock Osann 

 writes : " Das Yerbaltniss der Alkalien lasst das Gestein als 

 der Gruppe der andesitischen Trachyte nahestehend erkennen, 

 worauf auch die vereinzelten grosseren Sanidin-Einsprenglinge 

 hinweisen ; der hohe Kalk- und Kaligehalt gegeniiber den 

 geringen Mengen an Natron erklaren sich aus der Beobachtung, 

 das neben dem Sanidin ein basischer Plagioklas (Labrador) als 

 Einsprengling vorhanden ist. Vergleicht man die Analyse mit 

 derjenigen anderen andesitischer, theilwise Olivin fiihrender 

 Trachyte (Mte. Amiata, Arsostrom, Mte. Alfina) so fallt ihr 

 holier MgO-Gehalt auf (im Arsogestein trotz des Olivinge- 

 haltes nur 1*77 p. ct.), derselbe findet nur in der gleichzeitigen 

 reichlichen Anwesenheit von Biotitund rhombischem Pyroxen 

 seine Erklarung."f 



The augite-andesite from Mt. Fagos is " composed of plagio- 

 clase, diopside, and biotite, with accessory magnetite, apatite, 

 and zircon, lying in a glass base." J The plagioclases are labra- 

 dorite, but there are possibly a few orthoclase microlites in the 

 ground mass. 



The Gleichenberg trachyte contains, according to Hussak, 

 large sanidine phenocrysts, fewer and smaller ones of oligo- 

 clase, biotite, and dark augite, in a globulitic base.§ 



The augite-andesite from Kara Tash has numerous pheno- 

 crysts of labradorite (a little more basic than AbjAnJ, pale 

 green diopside, some biotite, and grains of magnetite, in an 

 abundant trichitic, glassy base.| 



The biotite-dacite from Pergamonl" contains phenocrysts of 

 labradorite, with fewer sanidines, biotite, and olive-green horn- 

 blende. The rock is called a dacite on the basis of its chemical 

 composition, although containing no free quartz, thus again 

 illustrating the difficulties attendant upon a consistent minera- 

 logical classification of these intermediate rocks. 



* Journal of Geology, vol. iv, p. 838. 



f Beitrage zur Kenutniss der Eruptivgesteine des Cabo de Gata, II ; Zeitschr. 

 d.d. geol. Gesell., vol. xliii (1891), p. 720. 



\ Washington, On Igneous Rocks from Smyrna and Pergamon ; this Journal, 

 vol. cliii (1897). p. 43. 



§ Zirkel, Lehrbuch der Petrographie, ii, p. 383. 



I On Igneous Rocks from Smyrna and Pergamon ; this Journal, vol. cliii, p. 44. 



1 Ibid., p. 48. 



Am. Jour. Sci. — Fourth Series, Yol. V, No. 29. — Mat, 1898. 

 25 



