BAVARIAN BASALTS 
117 
an aluminium-magnesium silicate, containing much water. The 
name Magnalite is proposed for it. 
Another abundant mineral of the basalts is phosphorite. It is 
found either as a joint-filler, between columns or in the form of 
concretions in the basalt and its tuifs. Again, the mineral is ob¬ 
served in narrow dikes, crossing the compact basalt and decom¬ 
posing it on both sides. In some localities the basalt, thoroughly 
impregnated with phosphorite, is in a condition of complete decay. 
In a basaltic tuff there were found pieces of wood changed into 
phosphorite. Macroscopically, as well as microscopically, the wood 
structure was readily recognizable. In all the phosphorites ex¬ 
cept the amorphous forms of the mineral, occur small crystals of 
apatite. 
In the tuff, containing phosphoritized wood, silicified trees are 
found with well preserved cell structures. Without doubt hot 
springs, with a solution of phosphoric and silicic acid, followed 
. the eruption of the magma, decomposing the basalt and at the 
same time forming phosphorite and silica. 
Geologists quite generally use the term basalt, when referring 
to the extensive lava flows of Iceland, Scotland, and Ireland and 
the Deccan of India. But these eruptives differ wholly from 
the basalts, which are here described, because they contain common 
augite, not titanium-soda-augite; the amount of plagioclase is 
much greater; nephelite never is present. Their structure is not 
porphyritic but ophitic, and generally, the crystalline fracture 
enables one at once to distinguish these rocks macroscopically from 
the true basalts treated above. The name trap, now also in use 
for them, would be more appropriate than basalt. Furthermore, 
when such rocks have become porhyritic, the ground-mass showing 
an intersertal structure, they may be properly referred to as 
melaphyres, as noted by many geologists. Iddings applies the 
name basalt to andesites containing olivine, although the structure 
of these is not to be distinguished from labradorite-andesite. 
Consequently, if for these rocks the names trap, melaphyre and 
andesite are retained, there remain but comparatively few rocks 
to receive the designation of basalt. In fact, we are left with only 
those rocks which the early geologists had in mind, when they first 
applied the term basalt to them. 
To sum up, the rocks here under consideration have a por- 
