About Sapphire
Sapphire is a precious gemstone, a variety of the mineral corundum consisting of aluminium oxide trace amounts of elements such as iron, titanium, chromium, copper or magnesium. It is typically blue (due to titanium and iron), but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. The only color that sapphire cannot be is red – as red colored corundum is called ruby, another corundum variety. Pink colored corundum may be either classified as ruby or sapphire depending on locale. Corundum (Rubies and sapphires) has a hardness of 9 on the scale of Mohs.
An opal with a hardness of 6 will be rapidly covered with fine scratches and lose its polish if worn everyday as a ring stone. Quartz (hardness 7) is a component of dust and one of the most common minerals on Earth. Simply wiping off dust from a softer material will scratch it. The scratches may be tiny, even microscopic, but they’ll accumulate and become visible over time. On the other hand, a ruby or sapphire with a hardness of 9 will remain bright and lustrous for years because it’s harder than most of the abrasive particles that contribute to wear which makes it very suitable for all kinds of jewelry.