NOTE: If you can read this, then you have not entered our site from the proper entry point! In order for all links to function properly, you must start by clicking here.



Solid Solution

Complete Solid Solution occurs when two elements can substitue for each other completely in a mineral. Olivines 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 compostion 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.

The process of how this works is described on the next page.

The olivines are referred to as members of a complete solid solution series between the Magnetium (Mg) end member called forsterite, and the Iron (Fe) end member called fayalite. Mg-rich olivines are light green, and Fe-rich olivines are dark green or black. Olivines with intermediate compositions are intermediate in color. Their other physical characteristics also vary between those of the end members. In such minerals either pure end member is seldom found, though they may be synthesized in the laboratory.


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

Complete Solid Solution occurs when two elements can substitue for each other completely in a mineral. Olivines 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 compostion 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.

The olivines are referred to as members of a complete solid solution series between the Magnetium (Mg) end member called forsterite, and the Iron (Fe) end member called fayalite. Mg-rich olivines are light green, and Fe-rich olivines are dark green or black. Olivines with intermediate compositions are intermediate in color. Their other physical characteristics also vary between those of the end members. In such minerals either pure end member is seldom found, though they may be synthesized in the laboratory.


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 appropriate at 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



Last modified January 15, 1998 by the Windows Team

The source of this material is Windows to the Universe, at http://www.windows.ucar.edu/ at the University Corporation for Atmospheric Research (UCAR). © The Regents of the University of Michigan. Windows to the Universe® is a registered trademark of UCAR. All Rights Reserved. Site policies and disclaimer