40 
and eudialyte. The arfvedsonite builds thin, coal-black and 
shining prisms, usually not more than 2 millimeters long and 
with a breadth seldom more than one fifth of the length; they 
are arranged parallel to the schistosity and often produce a faint, 
silky lustre on the surfaces of schistosity. The felspar and the 
nepheline may be so fresh that they are colourless, and the rock 
then seems quite black; just as frequently they are white or faintly 
brownish white, being more or less zeolitised. The nepheline 
is in erystals of the usual form averaging one or two millimeters 
in diameter. The felspar forms thin plates of similar length 
and arrangement as the arfvedsonite prisms. The eudialyte is 
in small brownish grains or crystals, which as a rule are a 
littler smaller than the crystals of the nepheline. 
More locally we find medium-grained or even coarse-grained 
varieties, which are connected by transitional forms with the 
fine-grained. In extreme cases the arfvedsonite prisms and the 
felspar plates may reach up to I centimeter in length and 
2 millimeters in thickness. Massive varieties which do not show 
any trace of schistosity or flow-structure are likewise of purely 
local occurrence. 
The green lujavrite — @girine lujavrite — has a glaring 
grass-green colour; its most conspicuous mineral component 
is ægirine in small needle-shaped crystals — they are rarely 
more than one to two millimeters long and 0'01—0'05 milli- 
meters thick. This mineral plays here the same role as the 
arfvedsonite in the black lujavrite. Nepheline, felspar and 
eudialyte appear in the same manner as in the arfvedsonite- 
lujavrite. Like the latter the green rock is fine-grained and 
schistose, to an even greater extent as a rule. A very con- 
spicuous difference between the two rocks arises from the fact, 
that whilst the first is even-grained, the ægirine-lujavrite con- 
tains relatively large crystals of arfvedsonite, which appear as 
black spots in the green mass. These arfvedsonite crystals are 
not ordinary phenocrysts, but enclose poikilitically all the other 
