| Silicon Oxide | Aluminum Oxide | Magnesium Oxide |
| Titanium Oxide | Zirconium Oxide |
| American Elements | Astro Met Inc. | China Tungsten |
| CoorsTek | Corning Incorporated | H.C. Starck |
| Parker Chomerics | Saint-Gobain Quartz PLC | Solvay Chemicals |
| Terio Corporation | Thermal Ceramics | Zircar Zirconia |