Any corundum without trace elements is colorless. Corundum with trace chemical impurities makes the gems we know. Chromium gives the red to rubies, sapphire has iron and titanium, you can get other colors using vanadium or different ratios. Gems are neat.
It’s why I switched to DuckDuckGo. At least there I can find the result in a few pages. Google doesn’t even respect operators anymore. Want to search for enterprise but don’t want car ads? Good luck finding captain Picard through all that nonsense.