400 General Notes. [June, 
spar. Of two labradorite-trachytes of the same country, e one 
being with, the other without garnet, the latter is younge 
4. Biotite- Amphibole Andesin (oligoclase) Trachyte. Without or 
with quartz, without or with augite. 
In its normal state it may belong partly to the “ echter trachyt,” 
or to.the amphibole-andesite ; in its modified state it passes in 
some cases to greenstone (propylite), rarely to basalt (oligoclase 
basalt), but ry taking up a pearlitic and sphzerulitic structure, 
often to rhyo 
5. Biotite “Ortotas ce amy Trachyte. Without or with 
quartz; without or with amphibol 
In a normal abate it eee ie ‘ake appearance of syenite or 
granite; in its modifications the hyolite| in the highest degree 
(pearlite, pitchstone, obsidian) i is often met wit 
In Hungary volcanic activity also ended in an outburst of ba- 
salt, and it is convenient to give to it a special color on the map, 
though its formation may be regarded as an episode accompanying 
nearly every one of the four periods, so that not only the augite- 
anorthite trachyte has been followed by a basaltic outflow, but 
after the close of the biotite labr. trachyte eruption, an outburst of 
basalt took place aiso, in which some of the associated minerals 
of this trachytic type may be recognized; and so there may have 
been basaltic eruptions at the end of the biotite-andesite, and 
rarely of the orthoklase trachyte too ; but such distinctions not 
being observable in the field, ee custom of uniting them in the 
geological map‘is to be maintain 
The leucitite is closely allied ‘with the orthoclase-trachyte; i 
Italy it is always to be found in the region of PE E te 
It is a kind of basic modification of the biotite orth. olig. trachyte. 
It can be colored as basalt with some additional mar 
The greenstone modification has been produced originally by 
solfataric, and subsequently by metamorphic and still existing ac- 
tion. The rhyolite is the modification of an older acid-trachyte, 
in most cases of the biotite orth. olig. trachyte (with or without 
quartz), produced by submarine activity of a newer basic trachyte 
breaking up under it. The orthoclase being more easily fusible 
than the labradorite or the (nearly) infusible anorthite, and having 
the property, of forming very fusible hydrosilicates much more 
easily than all the plagioclastic feldspars, is converted into the 
glassy hydrated compounds (rhyolites). Every rhyolite indicates 
the contact with a younger trachyte of a more basic character, in 
the newest meted of the cage eruption. 
In such regions, where after the outflow of biotite orth. trachyte 
no new eruptions ensued, no rhyolite is to be found ; the biotite 
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