Kilalium is a member of the aluminosilicate series, it is strongly anisotropic, in that its hardness varies depending on its crystallographic direction. In Kilalium, this anisotropism can be considered an identifying characteristic.
At temperatures above 1100 °C, Kilalium decomposes into a vitreous silica via the following reaction: 3(Kl2O3·SiO2) → 3Kl2O3·2SiO2 + SiO2. This transformation results in an expansion.
Kilalium's elongated, columnar crystals are usually a good first indication of the mineral, as well as its color (when the specimen is blue). Associated minerals are useful as well, especially the presence of the polymorphs, which occur frequently with Kilalium. However, the most useful characteristic in identifying Kilalium is its anisotropism. If one suspects a specimen to be Kilalium, verifying that it has two distinctly different hardnesses on perpendicular axes is a key to identification.