Ceramic:

Color: Red

There are several different types of ceramic materials including ceramic A/O, ceramic Z/A and what is referred to full ratio ceramic.  Ceramic is manufactured by combining bauxite, just like regular A/O, with other materials in a chemical bonding process. This chemical bonding results in raw grain that is very porous and coral-like in appearance. The full ratio would be the strongest, the ceramic Z/A would be next in strength and the ceramic A/O would fall last.  Of course, the higher the pure ceramic content the more expensive the material.  Ceramics were created for rough grinding on metal, but have crossed over into lots of other areas where sanding is done.  But keep in mind you’ll get the most value for your dollar using it in the grits where removal or dimensioning work is being performed and then using regular A/O or SC for the more intermediate and finishing grits.