112 NEW YORK STATE MUSEUM 



more commonly as veins which are regarded as having a somewhat 

 different origin than the magnetites. 



Kiruna with its three great ore zones, Kiirunavaara, Luossovaara 

 and TuoHuvaara, easily ranks first among the Swedish magnetite 

 districts. To Kiirunavaara must be conceded the credit also of 

 being the largest accumulation of this ore of which we have any 

 certain knowledge. The single deposit is estimated to contain more 

 than one-half of the total available ore in Sweden, which is figured 

 at 1 158 millions of tons and recent magnetometric surveys indicate 

 a greater extension of the mass than had been previously taken into 

 account. 



The three ore zones referred to outcrop on the summits of as 

 many ridges which rise rather prominently above the Lapland pla- 

 teau. The Kiirunavaara deposit is a continuous tabular or sheetlike 

 mass forming practically the whole ridge of that name, which ex- 

 tends 3.5 kilometers north and south, and running under the lower 

 ground at each end so as to give a total length of more than 5 kilo- 

 meters. Its thickness ranges from a maximum of 164 meters to 50 

 meters or somewhat less, the higher points of the ridge showing 

 the greatest width of ore. It inclines at a rather high angle to the 

 east, disappearing under a mass of quartz porphyry. 



The ore occurrence at first sight seems in strong contrast with the 

 Gellivare type. The wall rocks are massive, porphyritic, and show 

 little or no effects of metamorphic influences. Their structures are 

 rather those of dikes or volcanic rocks than of intrusives which have 

 crystallized by slow cooling at great depths. But the more striking- 

 features relate to the ore itself, which has a dense steely appearance, 

 revealing no granularity or crystalline texture to the unaided eye 

 and breaking with smooth surfaces like basalt; the ore further- 

 more is practically pure magnetite, the whole mass averaging about 

 96 or 98 per cent of that mineral, with apatite as the only nonmetal- 

 lic ingredient of importance. Analyses sometimes run over 70 per 

 cent in iron. The distribution of the apatite is very irregular, so that 

 it has been found possible to extract in a large way several different 

 commercial grades of ore from the one deposit. The interesting 

 structures which develop out of the variable relations between the 

 magnetite and apatite have been described by Dr. O. Stutzer^ and 

 more fully by Doctor Geijer-. 



1 The Geology and Origin of the Lapland Iron Ores. Jour. Iron & 

 Steel Inst. II. 1907. 



- Geology of the Kiruna District, p. 88 ct scq. 



