Answers to Chapter 5 End of Chapter Questions
1. Why are some minerals stable several kilometers underground
but unstable at the earth’s surface?
The answer is due to weathering.
Many minerals are quite
thermodynamically “happy” in the high pressures, and hot and
relatively dry conditions within the earth.
However, exposure to
the relatively cold and damp climates on or near the earth
surface breaks these minerals down by either chemical
weathering (chemical reactions which decompose the mineral
into new chemical compounds) or mechanical weathering (the
physical disintegration or breaking up of the mineral into smaller
2. Describe what happens to each mineral within granite during the
complete chemical weathering of granite in a humid climate. List
the final products for each mineral.
Our granite will be made up of quartz, potassium feldspar, a little
bit of plagioclase feldspar, some muscovite, and a little bit of
Quartz is stable and survives as quartz throughout the
Potassium feldspar and plagioclase feldspar are unstable
and break down into clay minerals (see part D, Table 5.1).
In the case of potassium feldspar, K