What is the coating material of ceramic coated white fused alumina?

Ceramic-coated white fused alumina, commonly known as iridium-coated WFA. It is a high-grade abrasive grain made by applying a special coating process to white fused aluminum oxide and then calcining it. The ceramic coating significantly improves the toughness, hydrophilicity, and self-sharpening properties of WFA. Thus, it results in even better performance for cutting blades and other grinding wheels. The color of the coating varies depending on the coating material.

Yellow ceramic-coated white fused alumina: Cerium oxide
White ceramic-coated white fused alumina: Zirconia
Red ceramic-coated white fused alumina: Iron oxide
Blue ceramic-coated white fused alumina: Cobalt oxide
Green ceramic-coated white fused alumina: Chromium oxide