350 | VITI ISLANDS. 
from the specimens of basalt there collected, as they may have come 
from the coarse conglomerates, many of which consist of fragments 
ten to twelve inches in diameter. 
Minerals.—The rocks of these islands contain but few minerals and 
no ores of value. Decomposition of the basalt brings out a deep 
iron-rust tint, and often impregnates the waters around with a strong 
chalybeate taste, at the same time incrusting the soil with a rust- 
coloured coating. ‘This process has formed some deposits of bog-iron 
ore, of which small specimens were obtained. But I observed no 
evidence that beds exist which may become of commercial importance. 
No other metal was observed here excepting the minute crystals 
of sphene, (an ore of Titanium,) which have been alluded to on page 
347. ‘The rocks about Mathuata have often a coppery hue, but it 
arises from chloritic incrustations. 
The common minerals of basaltic regions, augite, chrysolite, and 
feldspar, are of frequent occurrence; and the first of these is found in 
very regular crystals, with well-defined and polished faces. They 
may be collected in large numbers at Livuka, on Ovalau, where they 
are imbedded in a basaltic conglomerate. A beautiful green sand 
was brought me by a native at Mathuata, which consisted of grains 
of chrysolite. 
The geodes and nodules in the amyedaloidal varieties of basalt 
contain the common forms of quartz, with stilbite, natrolite, and 
analcime; but none of these minerals were observed in elegant 
specimens. 
The islands afford some indications of the action of the seas upon 
their shores before they were protected by reefs. Yet the period is 
so distant that it is unsafe to fix with much assurance upon any 
particular facts; moreover, if these islands have again subsided in 
part, as seems probable, they have buried with them the abraded 
shores and their ruins. But we are persuaded that some results 
of this action may be detected in the numerous small islets, standing 
detached from the present shores, with which they are identical in 
geological structure. The island of Mali is, in fact, two islands: 
they are separated by a narrow passage, and stand but a short 
distance from the shore. The conglomerate and tufa are identical 
throughout, and it may be reasonably inferred, that the whole was 
once a long point, against which the waves of an ancient ocean acted, 
unparried by coral reefs. Near the summit of the outer island, about 
one hundred feet high, there is a neat circular well, fifteen feet deep 
