326 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
The third theory—that the ores are of direct igneous origin—has 
been maintained by Léfstrand, Hégbom, and Stutzer. According to 
them the ores are segregations of magnetite from the acid igneous 
rocks in which they occur. The segregation theory has been opposed, 
amongst others, by De Launay and Vogt. Thus, De Launay main- 
tains that the segregation would have been impossible in such fluid 
lavas as the Kiruna porphyrites, and is improbable, since there is no 
transition between the ore and the barren rock. 
The segregation theory has serious difficulties, and is faced by sev- 
eral obvious improbabilities. The ore occurs as a band nearly forty 
times as long as it is broad. It has the aspect, therefore, of a bed or 
a lode. The ore has not the granular, crystalline structure of an igne- 
eus rock like the hyperite of Taberg, but the aspect of a material 
deposited from solution or formed metasomatically. It is almost free 
from titanium, the undesirable constituent so abundant in the ores of 
Vaberg and Routivaara. 
The igneous theory can not, however, be hghtly dismissed, as it is 
supported by the high authority of Broteccer Ho6égbom, and therefore 
demands careful consideration. 
It has been advanced in two main forms, the one considering the 
ore to have been deposited at the time when the igneous rocks were 
consolidating, the other considering it was deposited at a later period. 
According to Professor Hégbom, the ore was syngenetic, being a true 
magmatic segregation from a syenite. But, according to Doctor 
Stutzer (1906), the segregation was later than the consolidation of the 
syenite. He describes the lode as an intrusive banded dyke, of which 
the chief constituents are magnetic and apatite; and the injection 
of this dyke pneumatolytically affected the rocks beside it, producing 
an intermediate zone impregnated with ore, which he compares to 
contact deposits.¢ 
In spite of the high authority of Professor Hégbom, I am bound to 
confess that the Kiruna ores do not impress me as of igneous forma- 
tion. Their bed-like form, microscopic structure, and poverty in 
titanium are features in which they differ from those admittedly due 
to direct magmatic segregation. The microscopic sections that I have 
examined suggest that both the magnetite and apatite were deposited 
from solution and later than the consolidation of ie underlyi ing 
@Tn a later paper, of which only a short abstract has been eoned! Doctor 
Stutzer, however, explains that ‘‘ the intrusion of the ore dyke was at relatively 
the same time as the formation of the syenite, and that the ores were formed 
by magmatic separations in situ, or as peregrinating magmatic separations (mag- 
matie veins and bedded streams).” He adds that “ pneumatolysis plays no 
inconsiderable role in the formation of these veins.” Doctor Stutzer’s position 
may be summarized as regarding the ores as collected by segregation, but depos- 
ited in their present position by eruptive after actions. 
