OLIVINE-BASALTS. 
105 
A basalt (431) from tlie foot of Castle Rock contains curious opaque white 
inclusions up to 2 inches in diameter. They appear to be fragments of sandstone 
caught up in the lava ; but if so they have suffered extreme metamorphism. The 
basalt has permeated them in thin black vesicular glassy veins. The inclusions consist 
of a hard, minutely vesicular, glass which is colourless except at the actual contact with 
the basalt, where it becomes brown and nearly opaque. The glass incloses a few small 
scattered irregular grains of quartz and felspar, and is crowded with minute needle-like 
microlites, and, nearer to the basalt, with larger needles of colourless augite, such as 
have been described in the case of sandstone metamorphosed by basalt.* 
The results of chemical analyses of the olivine-basalt (656) from near the Gap, and 
of a limburgite-like rock (326) from Ridge Road, near Winter Quarters, are as follows 
under I and II respectively f 
I. 
IA. 
II. 
III. 
IV. 
(656) 
mol. ratios. 
(326) 
(Graveneck) 
(Hiirtlingen.) 
Si0 2 
— 
42-14 
•098 
42*10 
41-17 
44-14 
TiO, 
= 
4-90 
•001 
4-93 
3-08 
1-34 
alo 3 
- 
14-95 
•140 
14-87 
13-24 
13-87 
Fe 2 0 3 
r 
2-90 
•018 
3-20 
3-50 
11-73 
FeO 
= 
9-71 
•135 
9-70 
12-50 
H- 
CO 
MuO 
= 
0-12 
0 • 07 
CaO 
= 
10-32 
•184 
10-03 
10-24 
10-80 
MgO 
= 
9-47 
•235 
8-88 
8-21 
7-23 
Na 2 0 
- 
3-27 
•053 
3-20 
2-57 
3-25 
k 2 o 
= 
1-80 
•019 
1-80 
1-G0 
1-54 
PA 
= 
0-40 
•003 
0-58 
0-53 
0-80 
H.,0 at 110° 
— 
0-12 
0-11 
H 2 0 above 100° 
= 
0 ■ 10 
0-12 
3-21 
1-87 
S 
= 
0-09 
C0 2 
= 
0-04 
Ol 
o 
o 
r-H 
100-31 
100-04 
101-41 
The two results are almost identical, showing that probably most of the limburgite- 
like rocks only differ from the other olivine-basalts by their much more glassy base, 
in which little felspar has been developed. 
For comparison with these results are given under III an analysis by Senfter of 
a “ hornblende-diabase ” of Devonian age from Graveneck, Nassau, which was described 
by Streng ; J and under IV an analysis by Sommerlad of a Tertiary hornblende- 
basalt from Hartlingen, Westerwald.§ The close similarity between I and III extends 
even to the very high percentage of titanic acid. 
Olivine-basalts were found on Mount Terror, at Cape Crozier (830, 222, 218) ; 
and near Winter Quarters, at the Sulphur Cones (383) accompanying the hornblcnde- 
* Dannenberg, Tschermak’s Min. Petr. Mitth., 1895, Bd. xiv, p. 53. 
t For discussion of the analyses see p. 119. 
t Streng, Ber. oberhess. Ges. f. Nat. u. Heilkunde, 22, 1883, p. 248. 
§ Sommerlad Neues Jahrb., 1883, Beil.-bd. ii, p. 165. 
von. i. 
P 
