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ritie mineral of rather strong double refraction, which has been 
formed to the cost of the pyroxene. 
The large extinction angles in sections normal to the obtuse bis- 
sectrix again point to a Na-content of the orthoclase of the micro- 
perthites. The analcite has been formed partly at the cost of the 
felspar, optic anomalies occur. The biotite is highly pleschroic, the 
colour ranging from brownish black to brownish-yellow. The py- 
roxene is almost colourless and is often encircled by a rim of green 
aegirine augite, but both -also occur separately. Biotite, pyroxene, 
titanomagnetite, titanite and apatite often are grown together, in these 
intergrowths all or some of the minerals referred to occur. 
Type 2. The felspars in this rock are partly green and the dark 
minerals chiefly occur only in small crystals. It was found in that 
part of the Serra do Gericino which is known as Serra de Cabucu, 
along the road between Mascarenhas and Cabucu. 
The felspars consist of orthoclase or microperthite, which is poor 
in plagioclase. Not a trace of felspathoids is distinguishable. The 
markedly pleochroic biotite (from brownblack to light brownish- 
yellow) has often partly or completely been converted into green 
mica, while at the same time grains of a light yellow-green highly 
refracting, isotropous mineral having the properties of garnet, are 
formed. These grains are also found scattered in the felspars and 
the conversion may have taken place already before the complete 
erystallization of the rock. 
The rock contains also titanomagnetite which has been entirely 
or partially converted into leucoxene. 
The dyke-, and the effusive rocks. 
We distinguish the following types of rocks: 
1. Alkalisyeniteporphyries. 
2. Nephdinesyeniteaplites. 
3. Tinguaites. 
4. Sölvsbergites. 
5. Trachy tes. 
Alkalisyeniteporphyries. 
If these rocks contained originally felspathoids, the latter have 
been completely converted into secondary minerals. 
Type 1. A rock, collected where the. road to the facenda D. 
Eugenia erosses the rivulet Cachoeira, contains white to bright 
reddish felsparphenoerysts in a grey fine-grained ground mass. 
The felsparphenocrysts consist of orthoclase in which felspar with 
stronger double refraction is seen in small quantities. Pseudomorphs 
