No. 7. J APATITE IN NORWAY. 433 



off-shoot with an especial zone, forms here a general larger zone 

 around the entire net, wherein the dark gabbro between the off- 

 shoots entirely disappears. The smaller veins of Ravneberg 

 behaved similarly to those of Regardsheien. The zone of 

 " spotted gabbro" is here usually about six inches thick on each 

 side, while that of the large gangstoch is much thicker. We 

 observed here that small stringers of hornblende (some of them 

 barren of apatite), hardly one cm. thick, were surrounded by as 

 broad a zone of '"'spotted gabbro" as the larger veins. Each of 

 the two other groups of veins of Ravneberg was surrounded by a 

 large portion of "spotted gabbro." 



The manner and method of the occurrence of "spotted 

 gabbro" in the deposits just described throws more light on the 

 Oedegarden deposit. 



We have studied this rock in close contact with the apatite- 

 bearing veins. On Oedegarden it is no longer every single vein 

 that is surrounded by an especial zone of " spotted gabbro." 

 The entire Oedegarden vein-system, with its numerous and large 

 veins, occurs in a small band of this gabbro. Only at a couple of 

 points could we discover the dark violet gabbro, which is else- 

 where so common in this region. The boundary between these 

 two varieties of gabbro is always tolerably sharp : on Regards- 

 heien we broke out hand specimens of medium size, one-half of 

 which consisted of the ordinary dark gabbro, and the other of 

 the spotted variety, while the centre was a transition stage be- 

 tween the two. In regard to the relation between the " spotted 

 gabbro" and the other neighbouring rocks, we observed on Oede- 

 garden that the labradorite sometimes, although very rarely,, 

 showed cleavage planes with twin-striping. In this case the rock 

 can only with difficulty be distinguished from the adjacent quartz- 

 free (oligoclase) hornblendic gneiss, all the more so because the 

 schistose texture of the latter is easily recognisable only at some 

 distance from the boundary of the gabbro. We ourselves there- 

 fore at first took the " spotted gabbro " of Oedegarden for a por- 

 tion of the gneiss altered by contact with the veins — which it 

 certainly cannot be. 



Besides the above-described deposits there are some others 

 known to occur in the gabbro ; but we had no opportunity to 

 examine them. 



