Just to be clear, chromium does not replace all of the aluminum when forming ruby. Chromium impurities replace 1-2% of the aluminum ions in the crystal structure, a very negligible amount.
Both sapphire and ruby are gem forms of corundum, Al2O3. When there are zero impurities, you get a clear, or "white sapphire". When you start adding trace amounts of impurities, you start to change the color of the gem.
Rubies get there red color from trace amounts of chromium impurities in the crystal structure. Sapphires, blue corundum, get their color from trace titanium impurities in the crystal structure.
Sorry, just a geology nerd needing to clarify!
Source:
https://geology.com/gemstones/ruby-and-sapphire/
I would love to pick up a sapphire/ruby insert for my 30mm banger at some point, just not in the cards right now. Til then, I'll just keep it loaded up with sapphire/ruby pearls/steamrollers!
Still calling bulllshit on Adapt Tech's claims about their (blue) sapphire!