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.
