228 ALBERT JOHANNSEN 



The name is now generally applied to peridotites with olivine and 

 much diallage or augite, although the type rock actually contains 

 considerable hornblende and belongs to Family 3, 6, or 10. 



Harzburgite Rosenbusch^ and saxonite Wadsworth^ were 

 applied to peridotites composed of olivine and a monoclinic pyrox- 

 ene. Vogt,^ following Brogger, uses saxonite for the iron-poor 

 oKvine-enstatite rocks and harzburgite for the iron-rich members. 

 A saxonite from Minnesota, described by Hall/ consists of enstatite 

 60 per cent, olivine 35 per cent, and ores 5 per cent, consequently 

 belongs to (42 11). 



Families 7 and g. — These are the families of the olivine-free 

 amphibole-(or biotite-)pyroxene rocks. Here belong Cromaltite 

 Shand,s consisting of aegirite-augite 51.9 per cent, melanite 

 15.6 per cent, biotite, apatite, and ores. Its number is (429). 

 A hornblende-hypersthenite, named bahiaite by Washington,^ with 

 the percentages h5^ersthene 46, augite 5, hornblende 40.7, and 

 ores 8.3 (rock number 429), also belong§ here. Washington says 

 olivine is neghgible in bahiaite, but one such rock described by 

 him'' contains 7 . 5 per cent, which places it in Family 10. 



Family 8. — This is the family of the amphibolites and horn- 

 blendites. Among these is a hornblendite from Brazil, described 

 by Washington.^ It consists of hornblende 91.6 per cent, olivine 

 3 . 6 per cent, and magnetite 5 . i per cent. 



'H. Rosenbusch, Mikroskopische Physiographic der massigen Gesleine (2d ed.; 

 Stuttgart, 1887), p. 269. 



*M. E. Wadsworth, Lithological Studies (Cambridge, Mass., 1884). 



3 J. H. L. Vogt, "Beitrage zur genetischen Classification der durch magmatische 

 Differentiationsprocesse und der durch Pneumatolyse entstandenen Erzvorkommen," 

 Zeitschr.f. prak. Geol. (1894), p. 384, note. 



4 C. W. Hall, "The Gneisses, Gabbro-Schists, and Associated Rocks of South- 

 western Minnesota," U.S. Geol. Surv., Bull. 157 (1899), p. in. 



sS. J. Shand, "On Borolanite and Its Associates in Assynt," Trmis. Edinburgh 

 eol. Sac, IX (1910), 394. 



^ Henry S. Washington, "The Charnockite Series of Igneous Rocks," Amer. Jour. 

 Sci., XLI (1916), 331-32. 



7 Ibid., "An Occurrence of Pyroxenite and Hornblendite in Bahia, Brazil," Amer. 

 Jour. Sci., XXXVIII (1914), 86. 



8 Ibid., p. 82. 



