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The Process of forming a rock from a Solid Solution Melt

Complete Solid Solution occurs when two elements can substitue for each other completely in a mineral. Olivines, as a mineral group, are excellent examples of this type of solid solution. Forsterite, Mg2SiO4, and fayalite, Fe2SiO4, have identical structures because the ions Mg2+ andFe2+ are very nearly the same size and are chemically similar. If both iron and magnesium are present in the environment of crystallization, a single mineral with a composition intermediate between forsterite and fayalite will form. This mineral is considered to be a "solution" of fayalite and forsterite. Because minerals with all possible intermediate compositions can be formed, the formula is written (Mg,Fe)2SiO4, and the general name, regardless of Mg:Fe ratio is olivine.

This drawing illustrates how a pool of melted magma can form various kinds of silicate rocks.
Click on image for full size version (40K GIF)

Go to a listing of Rocks by mineral group

Solid Solution

Not applicable for this reading level.

This drawing illustrates how a pool of melted magma can form various kinds of silicate rocks.
Click on image for full size version (40K GIF)

Go to a listing of Rocks by mineral group

Solid Solution Example

Not applicable for this reading level.

This drawing illustrates how a pool of melted magma can form various kinds of silicate rocks.
Click on image for full size version (40K GIF)

Go to a listing of Rocks by mineral group