Metal-coated crystal

Possible coatings include gold, indium, titanium, niobium and copper.

Such products are created in a vacuum chamber by vapour deposition.

[1] Gold sublimation (phase transition) occurs, the resulting vapor depositing onto the crystal's surface.

When viewed under a gemological microscope in diffused direct transmitted light, aqua aura displays the following properties:[2] The brilliant color of these products is the result of optical interference effects produced by layers of metal.

[3] Media related to Aqua aura at Wikimedia Commons