In this work, the use of a natural yttrium oxide and rare earth oxide solid solution (CRE₂O₃) as stabilizers of the α-Si₃N₄ phase to form α-SiAlON has been investigated. This oxide mix is produced at FAENQUIL-DEMAR, at a cost of only 20% of pure commercial Y₂O₃. Two α-SiAlONs using pure Y₂O₃ or CRE₂O₃ have been prepared, using mixes of 20% by volume of a molar fraction of 9:1 of AlN to Y₂O₃ or AlN to CRE₂O₃, respectively, with 80% α-Si₃N₄. Samples were gas pressure-sintered at 1900 °C, under 1.5 MPa of N₂ for 60 min. Both compositions yielded α-SiAlON ceramics with high relative densities (98% t.d.), hardness of 18 GPa and fracture toughness of 5 MPa m^1/2, with homogeneous microstructures composed of elongated α-SiAlON grains with aspect ratios of 5. It is concluded that the mixed rare earth concentrate (CRE₂O₃) can be used to produce α-SiAlON ceramics with similar microstructures and mechanical properties of α-SiAlON ceramics fabricated using pure Y₂O₃, but with the advantage of its lower production cost.