Visually, there is hardly any difference between a sapphire crystal and a mineral glass. If, however, the specific material properties are considered, large differences can be observed. In contrast to the mineral glass, which resembles the quartz in its chemical structure, the sapphire glass is made synthetically and consists of high-purity aluminum oxide. A sapphire glass has a hardness of nine, which corresponds exactly to that of the natural precious stone sapphire, from which the name for the glass was derived. Mineral glasses have only degrees of hardness of six to seven. Due to the material properties, sapphire glass is extremely resistant, scratch-resistant and is also particularly resistant to breakage. Despite heavy usage a sapphire glass still looks like after the first day.