Metal-coated crystal

Metal-coated crystals are artificial products made by coating crystals, such as quartz, with metal to give them an iridescent metallic sheen. Crystals treated this way are used as gemstones and for other decorative purposes. Possible coatings include gold, indium, titanium, niobium and copper. Other names for crystals treated in this way include aqua aura, angel aura, flame aura, opal aura or rainbow quartz.

Aqua aura, crystals coated with gold fumes
A flame aura pendant set in silver.

Production

Such products are created in a vacuum chamber by vapour deposition. Quartz is heated to 871 °C in vacuum, and golden wire is heated to even higher temperature, either by resistive heating with direct electrical current, or by magnetron.[1] Gold sublimation occurs, and subsequently deposition on crystal's surface.

When viewed under a gemological microscope in diffused direct transmitted light, aqua aura displays the following properties:[2]

  • a coppery surface iridescence in tangential illumination
  • diffused dark outlines of some facet junctions
  • a patchy blue colour distribution on some facets
  • white facet junctions, irregular white abrasions and surface pits, where the treatment either did not "take" or had been abraded away.

The brilliant color of these products is the result of optical interference effects produced by layers of metal.

In culture

In 2015, American animated series Steven Universe introduced Rainbow Quartz, a personified fusion of two distinct gem characters: Pearl and Rose Quartz.[3]

See also

References
  1. "How is Aura Rainbow Quartz Made?".
  2. Robert Webster, Michael O'Donoghue (January 2006). Gems: Their Sources, Descriptions and Identification. ISBN 9780750658560.
  3. Gregson-Wood, Stephen (2019-11-27). "Unleash the Light is a Steven Universe RPG that's available now for Apple Arcade". www.pocketgamer.com. Retrieved 2023-07-27.

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