1945 
consisting of small muscovite-flakes, which may also be alteration 
products of original felspathoids. These, however, were then present 
only in a very smal] quantity. 
Umptekites. 
The Serra de Marapicu i.e. the Western part of the Serra do 
Gericino seems to be chiefly built up of these rocks. The composing 
minerals are for the greater part light-coloured microperthite and 
amphibole, and small quantities of pyroxene, titanite, analcite mag- 
netite and apatite. 
The felspars are microperthites with a variable amount of acid 
plagioclase, which is sometimes absent altogether. Large extinction 
angles in sections normal to the obtuse bissectrix point to a Na- 
content of the orthoclase. The amphibole differs from that of type1 
of the foyaites, the extinction-angles remain smaller and frequently 
varying colours occur in one and the same crystal; a greenish 
variety in the marginal zone, a brownish in the central part, but 
both varieties form separate crystals. The amphiboles are very much 
like those which Wricnr*) has described in an umptekite near 
Cabo Frio. In erystals of zonary structure we see in sections normal 
to the acute negative bissectrix of a small axial angle the following 
absorption: ¢ central part: reddish brown-green; margin: green) 
+ = 6 (central part: brown with a greenish tint; margin: brownish- 
green). 
In sections parallel to the plane of symmetry the extinction-angle 
increases towards the green marginal zone up to + 22°; we often 
see for the absorption parallel to the c-axis a homogeneous light 
yellow-brown colour, without any difference for central part and 
marginal zone. The only slight quantity of pyroxene consists of a 
green augite with extinction angles as high as 40° relative to the 
cleavage lines Apatite is present in numerous idiomorphic crystals. 
Pulaskites. 
This term comprises the alkali-roeks rich in mica, sometimes with 
a small amount of felspathoids. 
Type 1. The felspars have a more reddish tint than those of the 
rocks described above. The sample was collected along the road 
from Maxambomba to Mascarenhas, close to the facenda D. Eugenia. 
Biotite and titanite are visible macroscopically in numerous crystals. 
The composing minirals are: microperthite and a small amount of 
plagioclase, sodalite and analeite, biotite, augite with a margin of 
aegirineaugite, apatite and ore. As secondary product occurs a chlo- 
1) F. E. Wriaut. |. c. p. 246. 
