The transmitted light appears greenish-blue, because gold strongly reflects yellow and red. Such semi-transparent sheets also strongly reflect infrared light, making them useful as infrared (radiant heat) shields in visors of heat-resistant suits, and in sun-visors for spacesuits. Gold is a good conductor of heat and electricity. Gold has a density of 19.3 g/cm3, almost identical to that of tungsten at 19.25 g/cm3; as such, tungsten has been used in counterfeiting of gold bars, such as by plating a tungsten bar with gold, or taking an existing gold bar, drilling holes, and replacing the removed gold with tungsten rods. By comparison, the density of lead is 11.34 g/cm3, and that of the densest element, osmium, is 22.588±0.015 g/cm3. Color
Whereas most metals are gray or silvery white, gold is slightly reddish-yellow. This color is determined by the frequency of plasma oscillations among the metals valence electrons, in the ultraviolet range for most metals but in the visible range for gold due to relativistic effects affecting the orbitals around gold atoms. Similar effects impart a golden hue to metallic caesium. Common colored gold alloys include the distinctive eighteen-karat rose gold created by the addition of copper. Alloys containing palladium or nickel are also important in commercial jewelry as these produce white gold alloys. Fourteen-karat gold-copper alloy is nearly identical in color to certain bronze alloys, and both may be used to produce police and other badges. Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as green gold.
Gold metal was voted Allergen of the Year in 2001 by the American Contact Dermatitis Society; gold contact allergies affect mostly women. Despite this, gold is a relatively non-potent contact allergen, in comparison with metals like nickel.A sample of the fungus Aspergillus niger was found growing from gold mining solution; and was found to contain cyano metal complexes, such as gold, silver, copper, iron and zinc. The fungus also plays a role in the solubilization of heavy metal sulfides. See also
References
Further reading
Bachmann, H. G. The lure of gold : an artistic and cultural history (2006) online
Bernstein, Peter L. The Power of Gold: The History of an Obsession (2000) onlineBrands, H.W. The Age of Gold: The California Gold Rush and the New American Dream (2003) excerpt
Buranelli, Vincent. Gold : an illustrated history (1979) online wide-ranging popular history
Cassel, Gustav. "The restoration of the gold standard." Economica 9 (1923): 171-185. online
Eichengreen, Barry. Golden Fetters: The Gold Standard and the Great Depression, 1919–1939 (Oxford UP, 1992). Ferguson, Niall. The Ascent of Money - Financial History of the World (2009) online
Hart, Matthew, Gold: The Race for the Worlds Most Seductive Metal Gold : the race for the worlds most seductive metal"], New York: Simon & Schuster, 2013. ISBN 9781451650020
Johnson, Harry G. "The gold rush of 1968 in retrospect and prospect." American Economic Review 59.2 (1969): 344-348. online
Kwarteng, Kwasi. War and Gold: A Five-Hundred-Year History of Empires, Adventures, and Debt (2014) online
Vilar, Pierre. A History of Gold and Money, 1450 to 1920 (1960). online
Vilches, Elvira.