Expert: Joe Norris - 7/10/2009

Question
Does all stones contain iron minerals to some extent?


Answer
No, in fact iron (Fe) is rather far down on the scale at number 4 and composing about 5% of the chemical composition of the earth's crust.  The first ten elements and their percentages are:

Oxygen              @                46.6%
Silicone            @                27.0%
Aluminum            @                 8.1%
Iron                @                 5.0%
Calcium             @                 3.6%
Sodium              @                 2.8%
Potassium           @                 2.6%
Magnesiumn          @                 2.1%
Titanium            @                 0.4%
Hydrogen            @                 0.14%

The average chemical composition of igneous and sedimentary rocks are:

SiO2  59.14% in Ig       57.95% in Sed.
Al2O3 15.34              13.39
CaO    5.08               5.89
Na2O   3.84               1.13
FeO    3.80               2.08
K2O    3.13               2.86
Fe2O3  3.08               3.47
H2O    1.15               3.23
TiO2   1.05               0.57
P2O5   0.30               0.13
CO2    0.10               5.38
BaO    0.06                 -
SO3     -                 0.54
C       -                 0.66
______________________________
Totals 99.56              99.93