Treatments
We already have learned that heat treating certain varieties of amethyst and smoky quartz will produce citrine, irradiated amethyst turns it green and that irradiating white quartz can make it smoky, but what about the metallic and seemingly opalized colors? Fortunately due to its crystal structure macrocrystalline quartz doesn't take a dye well, but there is one special treatment that can turn an otherwise dull quartz crystal into an unusual beauty: vapor deposition. Simplified: individual quartz crystals or clusters are placed into a special vacuum chamber where they are coated with a thin film from vaporized elements that have been mixed with oxygen. The multitude of different colors and slightly metallic aurora borealis effects can be due to the following combinations that I have listed, along with some of their marketing names:
Aqua Aura, aqua blues: 24k gold
Imperial Gold, golden orange color: 24k gold, copper and titanium
Apple Aura, greens: nickel
Flame Aura, deep, opaque metallic rainbows: niobium and titanium
Opal Aura or Angel Aura, pastel AB: platinum and silver