In spite of the analogy to the electrostatics, the 3d colloidal nematostatics is substantially different both in
its mathematical structure and physical implications. The general tensorial structure of elastic multipoles
derived in Refs.[V. M. Pergamenshchik and V. O. Uzunova, Eur. Phys. J. E 23, 161 (2007); Phys. Rev. E 76, 011707 (2007)] allows
for a classification of different types of colloids in the nematostatics. The elastic multipoles consist of two tensors (dyads).
Based on this structure, I identify possible types of elastic dipoles. An elastic dipole is characterized by amplitudes of three
2 x 2 tensors and a two-component vector. The three coefficients describe dipole's isotropic strength, anisotropy, and chirality;
while the vector repersents dipole's longitudinal component. Besides the four pure types there are eight mixed types of elastic dipoles.
Possible symmetry groups of the director field related to the four dipolar types and their mixtures are found and described. The different
symmetries are illustrated by sketches of correspondent dipolar colloids. It is stressed that the azimuthal anchoring plays a nontrivial
role for the elastic multipoles. For instance, a helicoidal component of the surface anchoring easy axes of a colloid with the quadrupolar
shape symmetry can make it a chiral elastic dipole. Important particular cases of the dipole-dipole pair interaction potentials are
derived and discussed.
PACS: 61.30.Dk - Continuum models and theories, liquid crystal structure
PACS: 61.30.Jf - Defects in liquid crystals
PACS: 82.70Dd - Colloids
PACS: 01.55.+b - General physics