part 2] 



OF SOUTHERN EYEE PENINSULA. 



101 



It is notable for its high content of magnetite, although this 

 feature is not particulai'ly manifest in the specific gravity, owing 

 to the development of quartz and orthoclase in considerable 

 amount. The plagioclase has the composition of a calcic andesine, 

 and both felspars and quartz are crowded with fine needles of 

 apatite. On account of its rather abnormal composition, this rock 

 has been regarded as a critical one for analysis, which might be 

 expected to throw further light on its genesis. The accompanying 

 table embodies the analysis, with a number of other analyses 

 appended for com2mrison. 



; 



I. 



II. 



' in. 



IV. 



V. 



SiO., 



Per cent. 

 55-23 



13-02 

 7-66 

 6-60 

 2-27 

 5-87 

 2-80 

 2-93 

 0-15 

 0-50 

 0-79 

 2-85 



Per cent. 

 56-20 

 15-46 

 1-54 

 9-76 

 1-83 

 5 39 

 2-78 

 2-56 

 0-16 

 0-59 

 1-13 

 2-25 

 0-37 



Per cent. 

 56-17 

 13-62 

 7-46 

 7-81 

 3-43 

 6-52 

 3-09 

 0-83 



1 1-09 



Per cent, 

 56-78 

 14-33 

 5-76 

 9-27 

 1-58 

 5-26 

 3-43 

 1-75 

 0-33 

 0-10 

 0-36 

 1-44 

 0'25 



Per cent. 



57-21 



12-99 



3-28 



10-18 



1-59 



5-97 



3-07 



1-61 



0-68 



1-63 



0-44 



1-72 



0-43 



AU)-i 



FeoOa 



FeO... 



MgO 



CaO 



NaoO 



KoO 



H..0 - . 



H2O+ 



PaO, 



TiOs 



Accessories 



Totals 



100-67 



10002 



100-02 



100-64 



100-80 







i 



I. Amphibolite. Point Boston, Eyre Peninsula (South Australia). 

 II. Quartz-gabbro. Clierokee County (Georgia). F. W. Clarke. Bull. U.S. Geol. 

 Snvv. 419 (1910) p. 38. 



III. Amphibolite. Langenfeld, Otzthal. F. Becke, Denkschr. K. Akad. Wis- 



sensch. Wien, vol'. Ixxv (1913) p. 184. 



IV. Diabase. Somerset County (New Jersey). A. H.Phillips, Amer. Journ. Sci. 



ser. 4, vol. viii (1899) p. 279. 

 V. Dial)ase. Kittitas County (Washington). F.W.Clarke, Bull. U.S. Geol. 

 Surv. 616 (1916) p. 461. 



The rock is remarkable for its high content of iron oxides, and 

 in particular that of ferric oxide. This finds its explanation in the 

 abundant presence of magnetite. 



A calculation of the norm shows that it consists of 



Quartz 1 5'36 



Orthoclase 17-23 



Albite 23-58 



Anorthite 14-45 



Diopside 8-36 



Hypersthene 2-92 



Magnetite 11-13 



Ilmenite 5-32 



Apatite I'SS 



99-90 



