Earth, Our Environment - Class Notes
Chapter 3, Minerals: The Building Blocks of Rocks - 10
Common Mineral Groups in Earth


The continental crust is composed primarily of eight elements: O, Si, Al, Fe, Ca, Na, K, Mg.


The basic building block of the silicates is the silica-tetrahedron.

[Study Figure 3.10 on page 56 of the text]

These tetrahedra can combine in chains, sheets, or complex three-dimensional structures to produce the silicate minerals that have a variety of properties.

[Study Table 3.3 on page 63 of the text

Important Mineral Groups

We classify minerals based on the anions involved in the compounds.


Silica-Oxygen anions


Metals (Fe, Al) with Oxygen e.g. Al2O3 &endash;> Ruby, Sapphire


CO32- anions (marine) Formed by marine life from elements in sea water.


Sulfur anions &endash; Form in oxygen-poor environments. e.g. PbS, galena.


Sulfur anions &endash; Form when oxygen is present. e.g. CaSO4´2H2O, gypsum.


Chlorine &endash; Salts, form by evaporation - NaCl, table salt.

Native Elements

Gold, Silver, Copper, etc. are rare, but precious.

Minerals in Earth

Earth's core is mainly iron and nickel with a small amount of a lighter element, perhaps oxygen or sulfur.

The Mantle is almost completely silicate, and is rich in magnesium. The minerals of olivine and pyroxene are most common, and an aluminum-bearing mineral. Three lines of evidence for upper mantle:

Earth has two types of crust - oceanic and continental.

Oceanic crust is composed of basalt, the result of partial melting of the mantle. It is rich in Mg, Fe, Ca, Al which are in the minerals olivine, pyroxene plagioclase feldspar.

Continental crust diverse, old, and composed of incompatible elements that do not fit well in the minerals stable in the mantle (K and Na). The elements are concentrated in low-density minerals such as quartz and feldspar.

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Prepared by: Charles J. Ammon
January 1997