THE METAMORPHIC ROCKS OF ADELIE LAND STILL WELL. 39 



Sphene is an abundant accessory mineral in most members of the series. It is 

 frequently idioblastic and normally contains a crystal of magnetite as a nucleus. 

 Specimen No. 5, where sphene does not possess this nucleus, is exceptional. The 

 magnetite development varies from small crystals to large individuals, comparable in 

 size with the hornblende, which are only coated with a thin rim of sphene. In the 

 latter case the iron ore may total 6 per cant. Magnetite may also appear without the 

 sphene. The occurrence is similar to the " titanomorphitokranz " of the German 

 petrographers*, where sphene has recrystallised from decomposed ilmenite in 

 amphibolites. The magnetite has been described as such because of the highly magnetic 

 and polarised character of some separated grains, and because no violet colour was 

 obtained when an HC1 solution was reduced with tinf. In some sections a little red- 

 brown rutile is associated with the magnetite. Pyrite is occasional and sporadic. 



Colourless apatite becomes an important accessory in some cases. Its host is 

 usually, though not necessarily, the felspar. The crystals may be minute, but in its 

 best development we may get crystals comparable with the grain size of the rock. 



Lawsonite is an interesting constituent. Being a saussuritisation product it obtains 

 its best development in rocks with abundant saussuritised felspar, though it may also 

 form from hornblende. It is partly intergrown with biotite, and the lobated character 

 of the laminae is characteristic. It is partly in grains and partly in thin microscopical 

 veins. Occasionally the vein walls are lined with epidote while lawsonite forms the 

 main vein filling. In such cases the epidote has crystallised before the lawsonite. Both 

 the refractive index and the birefringence of the epidote are noticeably greater than 

 those of lawsonite in such instances. Calcite may form vein filling with the lawsonite, 

 and then lawsonite is found along the wall while calcite forms the centre. Calcite also 

 occasionally appears in coarse granular crystals. Fluorite appears in grains, or is 

 intergrown with biotite in the same manner as chlorite or lawsonite, while stilbite is 

 well developed in one example. Stilbite, fluorite, lawsonite, and epidote may be found 

 along joint planes and microscopic veins. 



The rock types may be summarised thus 



No. 153. Epidote biotite schist. 



No. 5. Amphibolite. 



No. 412. Biotite amphibolite schist. 



No. 720. Lawsonite mica amphibolite schist. 



No. 630. Quartz biotite amphibolite. 



No. 629. Amphibolite. 



No. 631. Amphibolite. 



No. 637. Amphibolite. 



No. 634. Amphibolite schist. 



No. 634A. Lawsonite amphibolite schist. 



No. 635. Lawsonite amphibolite schist. 



Op. cit., voL I, p. 74. 



t Since writing the above, some samples of iron ore from Cape Denison have been analysed by J. C. H. Mengaye, of the 

 New South Wale* Mine* Department. It has been found that the magnetic properties do not vary proportionately with 

 the titanium content. The more magnetic samples may have the higher TiOj value. 



