Colloidal gold preparations (suspensions of gold nanoparticles) in water are intensely red-colored, and can be made with tightly controlled particle sizes up to a few tens of nanometers across by reduction of gold chloride with citrate or ascorbate ions. Colloidal gold is used in research applications in medicine, biology and materials science. The technique of immunogold labeling exploits the ability of the gold particles to adsorb protein molecules onto their surfaces. Colloidal gold particles coated with specific antibodies can be used as probes for the presence and position of antigens on the surfaces of cells. In ultrathin sections of tissues viewed by electron microscopy, the immunogold labels appear as extremely dense round spots at the position of the antigen.Gold, or alloys of gold and palladium, are applied as conductive coating to biological specimens and other non-conducting materials such as plastics and glass to be viewed in a scanning electron microscope. The coating, which is usually applied by sputtering with an argon plasma, has a triple role in this application. Golds very high electrical conductivity drains electrical charge to earth, and its very high density provides stopping power for electrons in the electron beam, helping to limit the depth to which the electron beam penetrates the specimen. This improves definition of the position and topography of the specimen surface and increases the spatial resolution of the image.
New World Gold: Cultural Anxiety and Monetary Disorder in Early Modern Spain (2010). External links

"Gold" . Encyclopædia Britannica. Vol. 11 (11th ed.). 1911. Chemistry in its element podcast (MP3) from the Royal Society of Chemistrys Chemistry World: Gold www.rsc.org
Gold at The Periodic Table of Videos (University of Nottingham)
Getting Gold 1898 book, www.lateralscience.co.uk
Technical Document on Extraction and Mining of Gold at the Wayback Machine (archived 7 March 2008), www.epa.gov
Gold element information - rsc.org