We present you a reprint of a Tech Notes article written by Festool's David McGibbon:
Tech Notes No. 19/07
Sanding with gemstones
Have you ever wondered why Festool abrasives have names such as Rubin and Saphir? The abrasive grits used in most Festool abrasives are made from aluminum oxide… otherwise known as corundum. Most aluminum oxide used in industry is refined from bauxite, which is where we then get aluminum. Aluminum oxide crystals are extremely hard (hardness 9 on the mohs scale). Very few materials are harder other than diamond. Aluminum oxide can also reside in minerals found in nature. Did you know that ruby gemstones are actually aluminum oxide with just a trace of chromium to color them red? And sapphires are no more than aluminum oxide with traces of iron, titanium or other trace impurities? A sapphire can be clear, blue or any color other than red. Most sapphire gems are blue. Of course with gemstones, the value is in the looks and the appearance and quality of the rare naturally formed crystal.
So there we have it:
Ruby = Rubin Sapphire = Saphir
Just don’t try to talk your significant other into wearing Festool abrasives as jewelry. Although you might explain that it is manufactured from the finest material with the greatest care and precision. And with just a trace of chromium or titanium… who knows?