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Chapter II. 
THE BASEMENT-ROCKS OF SOUTH VICTORIA LAND. 
Crystalline Limestone. 
The crystalline limestones, which appear to constitute the prevailing rock of the 
Northern and Southern Foothills, are coarse-grained aggregates of calcite-crystals 
loosely held together. For the most part they are very pure, and show, in addition 
to the calcite, only a few small flakes of graphite and of a nearly-colourless phlogopite. 
Amongst the specimens, however, which were found by Dr. Wilson along Discovery 
Gulf, are fragments of crystalline limestone containing numerous rounded yellow crystals, 
which analysis has shown to be of chondrodite. The rock (see Fig. 69) is very 
similar in appearance to the chondrodite-limestones of Burma and Finland. 
Fig. 69. — Crystalline Limestone with Chondbodite, 
ebom Southern Foothills. (Natural Size.) 
Amongst the boulders found on the East of Mount Terror, just above the Barrier, 
is one of a schistose crystalline limestone, or calc-schist, containing quartz in fine grains 
in alternating bands with the calcite. 
Gneiss. 
Of gneisses there are not many specimens in the collection. They are gray and 
red foliated medium-grained rocks, some of which show conspicuous augen-structure. 
Like the Arctic gneisses of Greenland* these Antarctic rocks have the characters of 
metamorphosed granites and diorites (orthogneiss). They consist of orthoclase, 
oligoclase, quartz, biotite, and almost invariably hornblende. Microcline was not 
detected in any of the gneisses examined, but it occurs in large plates in a felspathic 
grit on Finger Mountain, which had obviously been derived from the decomposition 
of gneissic and granitic rocks. 
In the augen-gneiss, orthoclase generally forms the “ eyes ” which enclose biotite, 
idiomorphic oligoclase, and occasionally rounded blebs of quartz. f The “ eyes ” are 
mostly altered and red with oxide of iron. They are enclosed in a mosaic consisting of 
* Belowsky, Beit. z. Petrog. west. Nord-Gronlands, Zeit. d. deut. geol. Ges., 1905, Bd. lvii, pp. 15-90. 
f Evans, Quart. Journ. Geol. Soc., 1906, vol. lxii, p. 96. 
