no. 7.] apatite in norway. 425 



1. — Deposits in the Gabbro. 

 Oedegarden (Bamle District). 



This deposit, which is the richest at present worked, was dis- 

 covered in March, 1872. Its richness caused great speculations, 

 whereby the price of many deposits already known was raised 

 enormously, and in the districts wherein apatite occurs a genuine 

 apatite-fever was developed among the inhabitants. Up to 

 the date of our visit (in July 1874) it had already yielded, 

 according to the exact figures of the proprietor, over 3,200 tons 

 (of 2,000 lbs.) of the approximate value of $112,500. The apa- 

 tite has been shipped chiefly to England and Germany, and 

 recently to France and Sweden also. It is sold for £6 5 to 

 £6 6 stg. per ton. 



The veins of Oedegarden lie at the foot of a low rocky rido-e 

 running N. E. and S. W., which forms one side of a small valley, 

 whose centre is occupied by a little bog. The ridge consists of 

 hornblende rocks in highly inclined, not very distinct, strata, 

 chiefly hornblendic gneiss (the plagioclase white with twin-striping) 

 which is in part very poor in quartz. Sometimes the quartz dis- 

 appears entirely, and the rock becomes the diorite-slate of the 

 German lithologists. On the other side of the bog the same rocks 

 occur, alternating with ordinary gneiss and quartzite. At the 

 foot of the ridge there occurs a small zone of a light rock, without 

 a trace of cleavage or stratification. This rock is a peculiar 

 variety of gabbro, which we shall name " spotted gabbro." This 

 medium — to finely — granular rock consists, in varying propor- 

 tions, of brown lustrous hornblende (distinctly cleavable parallel 

 to the planes of the hornblende-prism) and white to greyish- 

 white labradorite. In the " spotted gabbro " the latter mineral is 

 without cleavage planes, compact or granular, with a splintery 

 fracture, lustre vitreous to slightly fatty, and in splinters translu- 

 cent. Its aspect recalls at the first glance quartz or moist snow. 

 Before the blowpipe it fuses somewhat more readily than ordinary 

 labradorite to a water-clear or milk-white glass. Hardness, 6, 

 sometimes a little less. An analysis made by S. Wlengell exhibits 

 the ordinary composition of labradorite : Si0 2 54.00, Al 2 3 

 (and a trace ot Fe 2 3 ) 24.13, CaO 7.89, Mg O 0.95; loss by 

 heating, 1.22 per cent. The alkali was not determined. 



The specific gravity of the ''spotted gabbro " varies somewhat 

 on account of its varying composition. A clear-coloured, cleavable 



