Kyanite is strongly anisotropic, in that its hardness varies depending on its crystallographic direction.

It is biaxial, so it has two optic axes and three indices of refraction n depending on the crystallographic direction.

Here, , and are the direction cosines of the domain magnetization, and , , those of the bond directions, towards the crystallographic directions.

In contrast, for anisotropic minerals, the velocity of light passing through the mineral varies with crystallographic direction.

Grain boundaries occur where the crystallographic direction of the lattice abruptly changes.

Since it is monoclinic, it has three different refractive indices, corresponding to the three crystallographic directions.

Amarantite is anisotropic, which means, the velocity of light varies with crystallographic direction, and there is more than one refractive index.

Which means that the velocity of light changes in crystallographic direction, this is easily identifiable in thin section.

The crystallographic directions are fictitious lines linking nodes (atoms, ions or molecules) of a crystal.

Nambulite is an anisotropic crystal, where the velocity of light that passes through the crystal varies depending on the crystallographic direction.