The Holmium oxide, with the CAS registry number 12055-62-8, is also known as Holmium(III) oxide. It belongs to the product categories of Rare earth; 67: Ho; Holmium Materials Science; Catalysis and Inorganic Chemistry; Chemical Synthesis; Holmium Metal and Ceramic Science; Nanomaterials; Nanoparticles: Oxides, Nitrides, and Other Ceramics Nanomaterials; Nanopowders and Nanoparticle Dispersions; Oxides; Metal oxide. Its EINECS number is 235-015-3. This chemical's molecular formula is Ho₂O₃ and molecular weight is 377.86. What's more, its systematic name is Holmium(+3) cation; oxygen(-2) anion. This chemical is stable at common pressure and temperature, and it should be sealed and stored in a ventilated and dry place. Moreover, it should be protected from moisture, air and acids. You should not breathe dust. When using it, you must avoid contact with skin and eyes. It is one of the colorants used for cubic zirconia and glass, providing yellow or red coloring. As most other oxides of rare-earth elements, holmium oxide is used as a specialty catalyst, phosphor and a laser material. 

Preparation: this chemical can be prepared as follows: the mineral mixtures are crushed and ground. Monazite, because of its magnetic properties can be separated by repeated electromagnetic separation. After separation, it is treated with hot concentrated sulfuric acid to produce water-soluble sulfates of several rare earth elements. The acidic filtrates are partially neutralized with sodium hydroxide to pH 3-4. Thorium precipitates out of solution as hydroxide and is removed. After that, the solution is treated with ammonium oxalate to convert rare earths in to their insoluble oxalates. The oxalates are converted to oxides by annealing. The oxides are dissolved in nitric acid that excludes one of the main components, cerium, whose oxide is insoluble in HNO₃. The most efficient separation routine for holmium oxide from the rare-earths is ion exchange. In this process, rare-earth ions are adsorbed onto suitable ion-exchange resin by exchange with hydrogen, ammonium or cupric ions present in the resin. The rare earth ions are then selectively washed out by suitable complexing agent, such as ammonium citrate or nitrilotracetate.