Zirconia Alumina:

Color: Blue or green

Z/A is a grain that takes the best characteristics of A/O & SIC and combines them together to create one very durable yet friable grain.  Its main ingredient is bauxite, just like A/O.  It is friable like SC but machine pressure is required to crack the A/Z grain where the SIC grain will fracture under simple hand pressure. Failure to achieve sufficient pressure to crack the A/Z grain will result in glazing of the abrasive and reduced life. The best of both worlds, this grain provides you with a consistently sharp edge on the workpiece and extended life. It is commonly seen anywhere high removal rates and time are factors, including planing of wood, heavy grinding of metal and other dimensioning type applications.  It is normally mounted on heavier paper or cloth backings and the grain itself is 15% – 40% more expensive to produce, so using it in the removal grits, 24 – 60, is where you will achieve more bang for your buck.