Rutile has a tetrahedral crystal structure (i.e. it has one fourfold axis) with 4/m 2/m 2/m symmetry.  Its structure is made up of parallel chains of octahedrons, which are in turn composed of a titanium ion surrounded by six oxygen atoms.  The model below shows the structure of the octahedron bases, although includes the unit cell edges.

It is the parallel chain structure of these octahedrons that produces the prismatic crystal habit typical of rutile.  The octahedron chains are arranged with the octahedrons on their “sides” and sharing opposing edges with other octahedrons.  The fourfold symmetry is a result of the square void created between the chains.  These voids and the general structure of rutile are shown clearly in the following diagrams.

NB:      If you move the mouse pointer over the two-dimensional octahedron structures you can see the arrangement of atoms.

Structure of Rutile – Viewed down the fourfold symmetry axis

Click on picture to see the arrangement of atoms within the structure

Structure of Rutile – Viewed from the side

    Click on picture to see the arrangement of atoms within the structure

Three Dimensional Structure of Rutile

 The structure of rutile is in fact very similar to that of a close-packed atomic structure. However, the close-packed oxygen sheets are slightly kinked (by about 20 degrees) to permit the fourfold symmetry.

The diagrams below are three-dimensional representations of the structure of rutile, showing the arrangement of atoms within the crystal. 

Rutile also occurs as slender acicular crystals when it is found in quartz, micas and corundum.

Rutile (Ti0₂) – Table of Structural data

The crystal data for rutile is tabulated below.

Twinning and Cleavage

(as described by crystal structure)

Another important characteristic of Rutile is its ability to twin easily (see Uses - Mineral Specimens and Gemstones).  Twinning is where two crystals appear to be growing out of (or into) each other as a result of an error during the crystallisation process.  Rutile twins with other crystals at an angle of 60 degrees on the {011} face, forming “elbow” shaped twins, cyclic twins of six or eight components and polysynthetic twins.  Polysynthetic twins are rarer than the other forms.

Prismatic cleavage of rutile, the formation of prisms, is distinct on {110} and indistinct on {100}.  Meanwhile there is poor pyramidal cleavage on {111}.

The TiO₂ Group

Rutile is a also a member of the titanium dioxide group which is composed of rutile, anatase, and brookite.  The crystal structures of these three minerals are shown below.

The crystal structure of rutile

The crystal structure of anatase

The crystal structure of brookite

Copyright © 2001 Andrew P.L. Robinson