Interactive · 2 questions
Silica: a hard, nonreactive, colorless compound that occurs as the mineral quartz and as a principal constituent of sandstone and other rocks.
Iron: a strong, hard magnetic silvery-gray metal, the chemical element of atomic number 26, much used as a material for construction and manufacturing, especially in the form of steel.
Obviously, iron is heavier and darker than silica. Therefore with this information, what do you think is the difference between igneous rocks with higher iron or other heavier elements content compared to those with a higher silica content?
Think about it.
Igneous rocks rich in Fe or Mg content is therefore darker in color. This kind of rock is called mafic.
On the other hand, igneous rocks with a higher silica content are called felsic rocks, generally lighter in color.
Looking at the rock above, does it seem to be mafic or felsic?
Let's try a few more examples.
Granite appears to have both dark and lighter (pinkish) colors. Is it mafic or felsic?