128 The America/i Geologist. August, i899 
sytc and anorthosyte-noryte. The feldspar is labradorite; ortho.rhom- 
bic pyroxene is the usual ferro-magnesian silicate, sometimes a little 
biotite occurs and occasionally augite, especially in the dikes; ilmenite 
and apatite sparingly. The chemical characteristics are high alumina 
(ca. 28 per cent.) and lime (ca. 10 per cent.), low iron (ca. 2 per cent.) 
and magnesia (0.3 per cent.) and a silica content of from 50 to 54 
per cent. Soda is to potash as 6:1. The structure is hypidiomorphic- 
granular except at the adamellyte contact, as later noted. The anor- 
thosyte consists practically wholly of labradorite of reddish color, 
while the anorthosyte-noryte shows iron ore and dark silicates, and is 
of violet hue. They were erupted at substantially the same time, as 
<hown by the gradual passage from one to the other, but at one 
locality a dike of the violet noryte has penetrated the anorthosyte. 
The Rekefjord and Soggendal Noryte. This area is bordered by 
anorthosyte on three sides, the sea on the fourth, and has an extent of 
21 km'. The central type is of quartz-gabbro-noryte becoming gab- 
bro-noryte toward the sides, the monoclinic pyroxene being less 
prominent than the orthorhombic. The rock contains apatite, ilmen- 
ite, hypersthene, augite, biotite and plagioclase. with hornblende, 
orthoclase and quartz in the central part. The feldspar of the gabbro 
noryte is labradorite wnth a little andesine; of the quartz gabbro 
noryte, andesine, albite and orthorclase in the proportion of 16: i: 2. 
The rock can be regarded as a differentiation product from the anor- 
thosyte marking a further step than the anorthosyte noryte, the SiO-, 
ALO3, CaO, and Na^O decreasing and the Fe^Oa, MgO, K.O, and PoOb 
rising. A dike apparently from the noryte penetrates the anorthosyte. 
It differs only in having ophitic structure. A small area of similar 
quartz noryte occurs on Hitteren island. 
The Monzonyte near Haekestad. This area comprises 78 km". 
The rock differs from the Rekefjord quartz noryte mainly in its higher 
potash, hence much microperthite. placing the rock in the orthoclase- 
plagioclase, rather than in the plagioclase series. Monoclinic pyrox- 
ene is more prominent than in the previous rocks, but the minerals 
are the same and the feldspar content is very large, showing the 
derivation of the rock from a highly feldspathic magma. Toward the 
periphery the rocks are more basic, becoming olivine monzonyte and 
gabbro noryte. This is the only occurrence of olivine in the entire 
eruptive area. 
A dike of the monzonyte penetrates the adjacent anorthosyte so 
that the former is the younger though the age difference is but slight. 
The dike rock varies from acid monzonyte in the center to noryte at 
the sides. 
The Adamellyte Area around Birkrem. This is regarded as a lac- 
colith with bronzite granite as the central type, grading through ada- 
mellyte and quartz noryte to noryte and anorthosyte noryte as peri- 
pheral faicies. Erosion has not proceeded far enough to uncover the 
granite except in a few of the deeper valleys. 
