Single crystals of -doped aluminoborates (YAB) and (GAB) have been grown by the top-seeded solution growth technique, and the optical absorption, photoluminescence and electron spin resonance (ESR) properties of dopants measured at low temperature. The optical absorption spectrum of comprises two broad bands with peaks at 514 and 576 nm in YAB and at 520 and 586 nm in GAB. The energy separation of the two bands in each crystal is due to the static Jahn - Teller splitting of the excited state of the ions. Photoluminescence from excited ions occurs as a broad band in the near-infrared region with a peak at nm in YAB and 754 nm in GAB when measured at 14 K. Both absorption and photoluminescence spectra are strongly polarized. The spin Hamiltonian parameters for ions substituting at trigonally symmetric sites in YAB have been determined from the orientation dependence of the ESR spectra. The measured shifts in the components of the g-tensor from the free electron g-value of 2.0023 are interpreted in terms of the mixing of the higher component of the ground states and of the excited state into the lowest ground state by spin - orbit interaction.