The dielectric constant of alumina is given in Table 19 as a function of temperature and crystal orientation. The dielectric constant increases slightly up to 500°C, and is quite dependent on orientation. Very low dielectric loss values for sapphire have been reported , but are questionable. With reasonable purity, loss tangents below 0.001 are likely. Actual values probably depend strongly on crystal purity.
Alumina is diamagnetic with a susceptibility less than 10-6 .