[244 
In the dark-grey leucite-tephrite one sees, macroscopically , phenocrysts 
of plagioclase and dark minerals few millimeters in diameter, the 
former contrasting little against the groundmass. Under the micro- 
scope it appears that the plagioclases have a well marked zonal 
structure, the augite crystals are light-green and often include numerous 
specks of ore. The little phenocrysts of biotite are sometimes strongly 
resorbed; the angle of the optical axes is very small, the pleochroism 
is strong from brown-black to light-yellow. The groundmass is 
composed of plagioclase with zonal structure, leucite (and some 
nepheline), green augite, a little biotite and much iron-ore. The 
latter mineral often obtains somewhat larger dimensions, without 
forming real phenocrysts. The leucite has likewise somewhat larger 
dimensions than the majority of the crystals in the groundmass. 
The porous light-grey rocks with gold-coloured pyroxene show 
numerous phenocrysts of white plagioclase (some as long as 0.75 ¢.m., 
but usually smaller) and smaller phenocrysts of the dark minerals in a 
groundmass which is either dense or micro-crystalline; in the cavities 
neogenie minerals have been formed. Under the microscope we see 
porphyrie crystals of strongly zonal plagioclase and gold-coloured or 
partly still green pyroxene, in a groundmass of strongly zonal plagioclase, 
gold-coloured pyroxene iron-ore, an isotropic, sometimes light-brownish 
substance, and a few little columns of apatite. Further a few rather 
large broad prisms hexagonal in cross section of an optically negative 
mineral with one optical axis, with a high refraction index, have 
been observed, which are slightly pleochroitical with «>> 0; they 
are almost colourless or tinged very lightly brownish, and include 
sometimes particles of a black or vermilion-red substance. A cleavage 
parallel with the axis of the prisms is indistinctly developed. in case 
originally some leucite has been present in this rock, the mineral is 
now altered into pseudomorphoses, on account of its feeble resistance 
against pneumatolytic agents. F 
Without entering into details about the metamorphosic and preneo- 
genic minerals found in these rocks, it can be mentioned that the 
aegirine-augites belong to different chemical combinations; we observed 
e.g. in sections parallel to (010) made across columns twinned accord- 
ing to (100), symmetrical extinctions of 14°, whilst several lath- 
shaped sections extinguish with angles of 20° to 30°; very small angles 
of extinction were equally observed. Black iron-ore, blue-black in 
reflected light, is found in great abundance in the rock, sometimes 
it surrounds as a border the aegirine-augites, which likewise can 
include the ore in great quantity. 
Moreover one sees elongated sections consisting entirely of black 
