GARNET
Suitable for sanding bare wood . Dulls quickly compared with man-made abrasives .
SILICON CARBIDE
Extremely hard; sharp enough to cut
glass, but wears quickly. Best for
smoothing joint compound and removing
dust nibs between coats of finish.
Extra-fine grits are used for wet sanding
the final finish coat .
ALUMINUM OXIDE
The jack-of-all-trades abrasive ; great for hand or power sanding on wood, paint, or metal . Not as sharp as silicon carbide, but lasts longer.
Excellent for sanding or polishing metal; too soft for other uses. Comes on flexible cloth backing .
CERAMIC
Tougher, more durable, and more expensive than other abrasives ; often bonded chemically with aluminum oxide . Used primarily on belts and discs for power sanding .
ALUMINA ZIRCONIA
An alloy of aluminum oxide and zirconium oxide. Sharp, hard, and durable, it cuts faster and lasts longer than aluminum oxide, but isn't as long-lived as ceramic. Found mostly on belts and discs for machine sanding.