Corundum is simply Aluminum Oxide, AL2O3. It is harder than any
other mineral except diamond. That is why is is such a wonderful abrasive.
It does not cleave, and it fractures cleanly with multiple facets, so when
put under load, it makes new faces that are sharp and cut well. This is very
useful when it is used as an abrasive, as when used to grind metal. When Corundum
is mostly or at least partly transparent, and has color, it forms one of many
different gems. The most common, and most valuable two are ruby, the red colored
Corundum, and Sapphire, which occurs in many other colors. One exceptionally fine
form of Corundum is called Emery. It is a black abrasive which is mined. The term
"Emery paper" used to describe papers which had actual Emery bonded to it. Another
form of Corundum abrasive paper is "Garnet paper", which, no surprise, has garnet
bonded to it. Both these papers are common in finer cabinet shops. However, if
you don't need the fine abrasive qualities of these papers, you can use good old
"Sand paper" which is paper with quartz crystals bonded to it. Corundum is easily
created in industry. That means that literally tons of small crystal aluminum
oxide crystals can be created. That is the secret of RealRuff® abrasive papers.
They have a process to create exceptionally fine crystals and a patented bonding
process that makes their papers some of the best in the industry.
Gwen's Glorious Gemstone Gallery
231 Lee Street