Many thanks go out to David Teter, Ph.D., of Teter Engineering, for contributing a great data set of elastic constants for some single-crystal oxides. 

Anisotropic single crystal materials have direction-dependent physical properties such as thermal expansion or elasticity that can't adequately be expressed by scalar values. This is why sometimes you will see a matrix of values for a material property on Citrination. Anisotropy is particularly important when a material must endure exposure to extreme forces, temperatures, or a combination of the two. Jet engine components, for example, often require specific engineering of crystal orientations to achieve performance targets. The list of mechanical properties and constants contributed by Dr. Teter is exactly the kid of data that we strive to have readily accessible to the community for efficient materials selection and development.