Where sapphire gets its blue tint mainly from iron, rubies get their pink to blood-red hue from chromium. So [NightHawkInLight]’s recipe starts with aluminum oxide grit-blasting powder and ...

transition metal spinel oxides formed on nickel-chromium-based superalloys. Unlike common lubricants that break down under high heat, spinel oxide maintains lubrication up to 700°C (1,292°F ...