THE METAMORPHIC ROCKS OF ADELIB LAND. 8T1LLWELL. 41 



The magnetite is placed above the sphene because the common magnetite nucleus 

 of the sphene sometimes appears idioblastic. Large crystals of magnetite, when not 

 enclosed in sphene. may be xenoblastic and penetrated by idioblastic epidote. Biotite 

 flakes, with their usual ragged ends, may penetrate the ragged ends of hornblende prisms, 

 but the idioblastic cross sections of hornblende exert their form against biotite. 

 Lawsonite is placed above biotite because it exerts its lobate outline against biotite. 

 Sometimes lawsonite shows crystalline boundary against hornblende and sometimes 

 the reverse is seen. Biotite and chlorite are inseparable ; so also are quartz and felspar, 

 as quartz is always a very minor quantity. 



5. CHEMICAL CHARACTERS OF THE CAPE DENISON AMPHIBOLITES. 



In order to determine the chemical characters of the series, examples of two extreme 

 members were selected for analysis. Nos. 153 and 629 have been, therefore, analysed 

 in the Victorian Geological Survey Laboratory by A. G. Hall, under the supervision of 

 P. G. W. Bayly. No. 153 is an epidote bidtite schist with biotite developed almost to the 

 exclusion of hornblende. No. 629 is an amphibolite in which hornblende dominates 

 very largely over the mica, and it was chosen for analysis because its outcrop contains 

 the remarkable xenoliths. Actually, its hornblende content is a little higher and its 

 mica content a little lower than in the most typical examples. Such variation finds 

 its explanation in the metamorphic differentiation that has occurred in this band. 



No. 153. No. 629. 



Si0 2 52-73 .. 48-74 



A1 2 S 13-99 . . 13-64 



Fe 2 s 4-31 .. 3-31 



FeO 9-19 .. 9-98 



MgO 3-27 .. 7-12 



CaO 5-98 .. 10-34 



Na 2 1-73 .. 1-96 



K 2 2-98 .. 0-83 



H 2 0+ 1-72 .. 1-95 



H 2 0- 0-10 .. 0-11 



C0 2 strong trace . . trace 



Ti0 2 2-14 .. 1-26 



ZrOj nil .. nil 



P 2 5 0-90 .. 0-14 



S0 8 nil .. nil 



Cl 0-08 .. o-04 



S 0-04 .. 0-06 



CrA 0-03 . . 0-05 



MnO 0-39 . . 0-35 



NiO, CoO 0-03 . . 0-01 



CoO trace trace 



