File:The Quarterly journal of the Geological Society of London (12711866234).jpg

1855..
FORBES — FOLIATION OF ROCKS.
171
Fig. 3. — Section of gneiss, limestone, and granite, at Stampekjtjern,
on the Heights above Christiansand, Norway.
W. E.
a, a. Gneiss. c, c. Bands of augitic gneiss in the limestone.
b, b. Foliated, crystalline, pink A, A. Granite (each band is about 10 ft. thick).
limestone.
30° to 45° East. The strike inclines in course of the foliation about
10° towards S.
The section here represented is E. and W. nearly, or at right
angles to the strike ; and, coming from the east, we have first the
gneiss, which sometimes is slightly granitic, but always preserves its
regular foliated structure ; — next we find a bed, about 14 feet thick,
of coarsely crystalline pink limestone, in which a beautiful foliated
arrangement is visible (as shown in the specimens now exhibited), by
the presence of numerous small crystals of a green augitic mineral and
white scapolite. Sometimes these minerals are so abundant as to
present a very striking appearance, at other times we have only single
lines of these crystals, with the intermediate limestone free from
them ; in all cases, however, both in this bed and throughout, they
arrange themselves in distinct lines, which are invariably parallel to
the lines of foliation of the gneiss itself. No tendency to split along
these hues is present. Next we have some small beds (c c) of what
may be termed gneiss, but in which the same augitic mineral appears
to replace the mica, giving the mass a green appearance. The beds
between this and the granite are of limestone, similar to the above,
but of white colour and foliated in the same way.
The granite (A), which now shows itself and is about 10 feet thick,
is composed of white felspar, quartz, and black mica, is coarse-grained,
and follows the general line of the beds. On its sides, where it
touches the limestone, it is in some places impregnated to a small
depth, but very strongly, with the same green augite ; and in cavities
at the junction we find aggregations of garnets, scapolite, and augite,
sometimes finely crystallized.
Beyond the granite we have beds of white limestone like the
former and similarly interstratified, if we may use the term, with beds
of augitic gneiss, until we again come to another and larger vein or
bed of granite, of similar character to the former band, and under