Editor's note: While its name gets tossed around and is even used as a synonym for “black,” real onyx is formed from bands of chalcedony in alternating colors, from pink/white to red/white to black/white. Kings have sat on black onyx thrones, there’s a beautiful theater in St. Petersburg that uses yellow onyx in its lobby, and many a chess master has marched onyx pieces across the board to victory. Get in on the trend with a cool Onyx wallpaper!