This work concerns ortho-borates according to the compositions InBO3:Eu3+, InBO3:Eu3+,Tb3+, and InBO3:Eu3+,Tb3+,Ce3+. All samples were investigated with respect to their structure type and spectroscopic properties. It turned out that InBO3 changes its crystal structure from calcite to high temperature vaterite by the incorporation of Eu3+ or Tb3+. At the same time, novel excitation bands arise caused by optical transitions originating from the presence of Eu3 + or Tb3+. The intensity of the D-5(0) -> F-7(2) transition of Eu3+ is enhanced due to the change of the crystal system. Doping Ce3+ into TbBO3:Eu3+ results in a complete change of the absorption spectra caused by the 4f-5d transition of Ce3+. These findings open up the possibility to employ the energy transfer chain Ce3+ -> Tb3+ -> Eu3+. Even though a metal-to-metal CT between Ce3+ and Eu3+ is well known to quench the photoluminescence of Eu3+, we found a quantum yield of about 50%.