Karl Petter sen — Geology of N. Norway. 391 



thickest of these masses forms the Gabbro field of Lyngen, extending 

 from the bottom of Balsfjord in a south and north direction, between 

 Ulfsfjord and Lyngenfjord, to a length of about nine geographical 

 miles, and with an average breadth of about one mile. The islands 

 of Kaagen, Arno, Seiland, and Soro are likewise traversed by con- 

 siderable courses of Gabbro. Moreover, Gabbro-like masses of a 

 more subordinate character break forth in the gneissoid granite of 

 the coast-tract. 



The land tracts formed of Gabbro are in the highest degree wild 

 and rugged. In this respect the Gabbro course of Lyngen is par- 

 ticularly remarkable, shooting up in an infinity of peaks and inac- 

 cessible pinnacles, of which some attain a height of about 2000 metres. 



The Felspar of the Gabbro is formed of plagioclase (Labradorite 

 and anorthite) — a form which G. Rose termed eucritic — some- 

 times of Saussurite (Saussurite Gabbro). The augitic element is 

 partly diallage, partly also hypersthene. Sometimes the rock may 

 also go over to a hornblende-gabbro. Olivine is a tolerably frequent 

 mixture. Magnetite, Titanic iron, and Pyrites are frequently found 

 in the rock ; sometimes also copper pyrites and apatite. 



A smaller mass of Gabbro breaking forth in the west side of the 

 great Senjen island is traversed by a thick vein of magnetic pyrites 

 mixed with copper pyrites. The magnetic pyrites contains here 

 2 to 3 per cent, of nickel. The important nickel works of Berg 

 are situated on this lode. Masses and courses of serpentine are 

 often connected with the Gabbro. The serpentine is here probably 

 only a transformation product of the Gabbro. 



4. Greenstone — sometimes more coarse-grained, sometimes fine- 

 grained — is frequently found connected with the Baipas group in 

 Alten and Kvoenangen, and on the island of Vanna, in the parish of 

 Karlso. The chief elements of the rock are hornblende and plagioclase. 

 The stone is often traversed by stripes of yellow epidote, sometimes 

 associated with calc-spar and scapolite. Mica, apatite, magnetic iron, 

 pyrites and copper pyrites are not seldom found as accessory minerals. 



The greenstone does not form, like the Gabbro and Hypersthenite, 

 deep mountain courses, but appears usually in a more subordinate 

 form, either in small hills, or breaking forth between the layers of 

 the Raipas group, and often covering the same in more or less plate- 

 like masses. 



o. Olivine rock — an independent rock — appears in two places in 

 the Arnt of Tromso, namely, on the high plateau immediately to the 

 north of Tromsdalstind, and also at Skutvik lake, on the peninsula 

 between Malangen and Balsfjord. In these two places it forms large 

 isolated hillocks of more than 30 metres in height. The olivine stone 

 is a beautiful rock of olive-green colour, inlaid with enstatite. It 

 exhibits everywhere a transition to serpentine. Also, greenish talc 

 may be found in the rock as a transformation product. 



6. Serpentine appears in various points in the tract here noticed 

 — partly as independent masses in isolated hillocks, and partly in 

 connexion with the Gabbro as a transformation product. Chromate 

 of iron is never observed in the serpentine here. 



