Black gold (Jewelery)

Black gold (Jewelery)

:"Note that "black gold" is also a slang term for crude oil."Black gold or 'grey gold' as it is sometimes referred to is a type of gold used in jewelry [cite web
title=Jewelery Technology
url=http://www.gold.org/jewellery/technology/colours/special.html
accessdate=2007-11-21] . Though gold is known for its warm yellow color it can be produced by various methods in differing colors ranging from white to black [cite
author=W.S. Rapson
publisher=Academic Press
title=Gold Usage
date=1978] . Black colored gold can be produced by various methods.
* Electrodeposition or Electroplating using black rhodium or ruthenium. Solutions that contain ruthenium give a slightly harder black coating than those that contain rhodium [cite web
title=Gold In Purple Color, Blue Color And Even Black Gold
url=http://www.newsletter.kaijewels.com/gold-colors.htm
accessdate=2007-11-21] .
* Patination by applying sulfur and oxygen containing compounds.
* Plasma assisted chemical vapour deposition process involving amorphous carbon, and controlled oxidation of carat gold containing chromium or cobalt.

More recently a laser technique has been developed that renders the surface of metals deep black. A so called femtosecond laser pulse deformes the surface of the metal forming nanostructures. The immensely increased surface area can absorb virtually all the light that falls on it and thus rendering it deep black [cite web
title=Ultra-intense laser blast creates true 'black metal'
url=http://www.physorg.com/news83342514.html
accessdate=2007-11-21] [cite web
title=Ultra-Intense Laser Blast Creates True 'Black Metal'
url=http://www.rochester.edu/news/show.php?id=2701
accessdate=2007-11-21] .

References


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