It crystallizes in the trigonal system, and its crystal structure is the same as that of corundum (Al2O3). It has a Mohs hardness of 5-6.5 and has a slightly lower specific gravity than titanium dioxide, with ilmenite weighing between 4.0 and 4.7 g/cm3. https://medium.com/@rokadevaishnavi51/understanding-the-mineral-ilmenite-its-occurrence-and-formation-c6c92cfc5dd6