Yttrium silicate, Y₂O₃.SiO₂

By heating a mixture of yttria (3 parts), silica (1 part), and calcium chloride (30 parts) for two hours in a wind furnace and extracting the mass with water, Duboin obtained monoclinic crystals of yttrium silicate, Y₂O₃.SiO₂, which in crystalline form and optical properties closely resembled the mineral gadolinite.