An alchemical onyx is an enhanced gem researched at level 107 Invention. Making it requires an onyx, 50 refined components, 50 fortunate components and 10 precious components at an Inventor's workbench. It can be smelted into several items, such as Luck of the Dwarves, Grace of the Elves, Passage of the Abyss, and Ingenuity of the Humans.
Assuming median Grand Exchange prices, making an alchemical onyx values each fortunate component at 641,211.86 coins. Note this doesn't take into account the cost of refined or precious components.