Aqua aura is a term used to describe a natural crystal that has been coated with gold fumes. It is created in a vacuum chamber from quartz crystals and gold vapor. The quartz is heated to 871 oC (1600 oF) in a vacuum, and then gold vapor is added to the chamber. The gold atoms fuse to the crystal's surface, which gives the crystal an iridescent metallic sheen. The process was awarded the United States Patent No. 6997014 on 14 February 2006. The process was invented by Steven F. Starcke, Ronald H. Kearnes and Keven E. Bennet. While the patent might have been given in 2006, this material has been produced by this method for dozens of years prior.
The patent says "The invention provides a decorative object comprising a transparent or translucent substrate having a body and at least one surface bearing a thin film coating. The coating imparts in the substrate a body color that appears substantially constant at different angles of observation. This body color is imparted in the substrate at least in part by absorption of visible radiation that is transmitted through said coating. The coating includes a high absorption layer comprising film that is highly absorptive of visible radiation. Also provided are methods of coating gems and other decorative objects, as well as methods of heat treating coated gems and other decorative objects."