llows:

PERCENTAGE OF COMMON MINERALS IN SHALE, SANDSTONE, AND LIMESTONE

-----------+----------+-----------+-----------
| Average | Average | Average
| shale | sandstone | limestone
-----------+----------+-----------+-----------
Quartz | 31.91 | 69.76 | 3.71
Kaolin | 10.00 | 7.98 | 1.03
White mica | 18.40 | |
Chlorite | 6.40 | 1.15 |
Limonite | 4.75 | .80 |
Dolomite | 7.90 | 3.44 | 36.25[1]
Calcite | | 7.21 | 56.56
Gypsum | 1.17 | .12 | .10
Feldspar | 17.60 | 8.41 | 2.20
Magnetite | | .58 |
Rutile | .66 | .12 | .06
Ilmenite | | .25 |
Apatite | .40 | .18 | .09
Carbon | .81 | |
-----------+----------+-----------+-----------
Total | 100.00 | 100.00 | 100.00
-----------+----------+-----------+-----------
1: Includes small amount of FeCO_{3}.

In comparing the mineral composition of igneous and sedimentary rocks,
it will be noted that the most abundant single mineral of the igneous
rocks, and the most abundant mineral of the lithosphere as a whole, is
_feldspar_; that next in order is _quartz_; and that third comes a group
of dark green minerals typified by augite and hornblende, commonly
called _ferro-magnesian silicates_ because they consist of iron and
magnesia, with other bases, in combination with silica. The sedimentary
rocks, which are ultimately derived from the destruction of the igneous
rocks, contrast with the igneous rocks mainly in their smaller
proportions of feldspars and ferro-magnesian minerals, their higher
proportions of quartz and white mica (sericite or muscovite), and their
content of kaolin, dolomite, calcite, chlorite, limonite, etc., which
are nearly absent from the unaltered igneous rocks. Evidently the
development of sediments from igneous rocks has involved the destruction
of much of the feldspars and ferro-magnesian silicates, and the building
from the elements of these destroyed minerals of more quartz, white
mica, clay, dolomite, calcite, chlorite and limonite. The composition of
the minerals of the sedimentary rocks is such as to indicate that the
constituents of the air and water have been added in important amounts
to accomplish this change of mineral character. For instance, carbon
dioxide of