322 JHE: ViOGE 
The phenomenon here discussed may, as to igneous rocks, be 
illustrated by Figure 1, representing a dunite from the Hestmando- 
field in the northern part of Norway, with an average of only 
about 1 per cent chromite. In some parts of the thin section 
chromite is entirely or almost entirely lacking, but in other places 
we may find aggregates of ten to twenty small octahedrons of 
Fic. 1.—Dunite from the Hestmandé-field, northern Norway. Groups of 
octahedrons of chromite, illustrating “together-swimming” or synneusis structure. 
(Photo. 25:1.) (Black=chromite, white =olivine.) 
chromite which, as well with reference to the idiomorphism against 
the olivine as with reference to the together-swimming structure, 
must have crystallized while the olivine was still in a molten 
condition. From this and other dunite rocks with a little chromite 
we may draw the conclusion that the chromite commenced crystal- 
lizing earlier than the olivine, when there was at least 1 or 0.5 
per cent, perhaps only 0.33 per cent, chromite present. But 
