
= ——_ | = “=” — = — "2s +e" 
230 STRUCTURAL AND FIELD GEOLOGY 
usually rich in ferromagnesian minerals (hornblende, rhombic pyroxene, 
and olivine), which are not infrequently accompanied. by biotite, apatite, 
green spinel, and various sulphides (pyrite, pyrrhotite, and chalcopyrite). 
Cab) Fai mat ae 

FIG, 80.—SECTION AT BLAAFJELD. (Vogt.) 
L, Labradorite-rock ; N, Norite-pegmatite; I, Ilmenite. Length of Section 600 metres.* 
Ilmenite (titaniferous iron-ore) occurs in some Norwegian gabbros under 
similar circumstances (Fig. 80), the ore-aggregates either forming an 
abrupt junction with the 
mother rock or graduating 
into it in the same way 
as titaniferous magnetite. 
Chromite is a frequent con- 
stituent of peridotites, and 
now and again so largely 
abounds that the rock con- 
taining it is mined. At 
Hestmand6, in Norway, for 

ay, 
py Ui hig 
TG: OH 
/ Vy, : / {lj 
YOY 

| }') example, the rock exploited 
: Ui is composed essentially of 
yp We olivine, enstatite, picotite, 
Vy My A andchromite. Tin-ore (cas- 
uy Vy WY 1/18 / siterite) likewise occurs as a 
5 y i primary constituent of many 
0 granites, but only in scat- 
tered grains and thin veins. 

* The Labradorite-rock 
(gabbro) contains some 2 
per cent. ilmenite, 4 per 
cent. ferromagnesian mine- 
rals, and 94 per cent. fel- 
spar ; the Norite-pegmatite 
Fic. 81.—SKETCH-PLAN OF MEINKJAR, yields 4o per cent. ilmenite, 
Norway. (After Prof. Vogt.) 35 per cent. ferromagnesian 
s, gneissose rocks; 1, hornblende-schist; , norite minerals, and 25 per cent. 
with inclusions of gneiss (xenoliths); 0, ore; h he Naw 
A, B, sections across the area, from east to west. felspar. Where the Norite- 
pegmatite graduates into 
the Labradorite-rock, the percentages are as follows :—6 to 18, ilmenite ; 
8 to 16, ferromagnesian minerals ; and 56 to 66, felspar. 

sn lie i Ail all ta ae 

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