82 



NATURE STUDY IX SCHOOLS. 



Here is a very brief list of some granites, just to give an idea of the 

 variety that is possible. 



Binary granite. Composed of quartz and feldspar. White in color. 

 Binary hornblende granite. Composed of feldspar and hornblende. 

 Binary micaceous granite. Composed of feldspar and mica. 

 Syenite granite. Composed of feldspar, mica, and hornblende, 

 (-iuartzose granite, Composed of quartz, feldspar, and mica, in fine grains. 

 Quartzose granite (coarse) Composed of quartz, feldspar and mica. 

 Keel granite (fine) Composed of quartz, red feldspar and hornblende. 

 Ked granite (coarse) Composed of quartz, red feldspar and hornblende. 

 Quartenary granite. Composed of quartz, feldspar, mica and hornblende. 

 Iron granite. Composed of the usual material, but much stained with iron. 

 Decomposing granite. Composed of the usual materials, but disintergrating 

 through the decomposition of the feldspar. 



Graphic gianite contains hornblende that has assumed irregular forms, many 

 of which resemble the letters of some anci3nt alphabets. See fig. t34. 



Fig. 34. 



Graphic Granite. 



It is easy to see that if we have these four constituents in the rock 

 at once we have, for instance, quartenary granite. If nature withholds one 

 or two of these ingredients, we have a different kind of granite. So also, 

 if the particles be fine or coarse, or irregularly distributed in the mass, we 

 have a decidedly different appearance, although the composition of the rock 

 is the same. Thus it is possible to have several specimens of rock ar- 

 ranged along a museum shelf, all differing from one another in appearance, 

 but having the same chemical composition. Granite for building purposes 

 should not contain too much iron, or at least the iron should be so com- 

 bined that it will not readily oxidize and look dingy. 



