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VI. Leueitebasalt. Bongsberg near Pelm. Eifel. Anal. E. Hussak cf. 
E. Hussak Sitz. Ber. K. Akad. der Wiss. Wien Vol. 77 1.1878. 
VII. Biotitelencitebasalt Pangkadjene. South Celebes. Anal. Dr. 
Bruhns cf. H. Bucking. Ber. der Naturf. Ges. zu Freiburg 
Iddings * *) already mentions the intermediate place, which the chemical 
composition of biotite occupies between that of olivine and felspar; 
the biotite molecule can be split into olivine and the oxide molecules 
necessary for the formation of felspar or felspatoids. It follows 
from this, in conjunction with the analyses quoted above, that in 
rocks of certain chemical composition where the proportions are 
favourable to the genesis of these minerals, the latter may show a 
large difference in relative proportions, whilst the conditions of crystal¬ 
lisation are but slightly different. Secondary biotite may be readily 
formed in these and in closely related rocks. 
Loss on ignition. 
*) J.P. Iddings. The origin of igneous rocks. Bull. Phil. Soc. Washington. Vol. 
AI1 1892. p. 166. 
