NOTES ON ANTARCTIC ROCKS. 481 
Basic Tuff, (No. 8a, 8b). 
A hardened tuffaceous material, light-brown in colour, contain- 
ing numerous darker angular fragments. Under the microscope 
is seen to be composed of numerous irregular fragments of various 
basic volcanic glasses. These vary in colour from light to dark 
brown, and are all amygdaloidal, the vescicles being filled or 
partially filled with colourless isotropic material. Some of the 
lighter fragments are almost pumiceous in texture, while a few 
consist of almost compact dark brown glass. 
All the fragments contain minute lath-shaped felspars with a 
parallel arrangement in each piece, while the more glassy ones 
contain trichites in addition. The matrix is comminuted material 
of the same nature as the fragments, and contains a wie tas, 
, angular pieces of felspar. 
No. 8¢ is very similar to the foregoing but is more porous, the 
vesicles being without amygdaloidal infillings. 
Nos. 12 and 15 are fragments of scoriaceous lavas, some of 
which approach pumice in character. They are probably of 
intermediate composition, but have not been examined in 
il 
Mica Schist, (No. 5.) 
A fine grained rock, consisting of quartz and dark brown mica, 
_ strongly marked schistose characters and easily fissile. In 
thin sections the rock appears to be made up principally of clear 
—— of quartz and flakes of biotite (Plate 14, fig. 4). The 
biotite forms about 20% of the whole mass and is perfectly fresh 
Bees strongly pleochroic. In addition to these constituents there 
‘Sasmall amount of a white mica which appears to be muscovite. 
There are also numerous small but beautifully formed prisms of 
brown tourmaline as well as zircon, apatite, magnetite, some 
Pseudomorphs of pyrites in oxide of iron, and a few grains of a 
— Spinel, probably pleonaste. Some felspar is also present, 
and possibly a member of the scapolite group. 
Ee—Dec. 4, 1995, 
