Less commonly, addition of manganese, aluminium, indium and other elements can produce more unusual colors of gold for various applications., which is also its only naturally occurring isotope, so gold is both a mononuclidic and monoisotopic element.
Thirty-six radioisotopes have been synthesized ranging in atomic mass from 169 to 205.
Gold often occurs in free elemental (native) form, as nuggets or grains, in rocks, in veins, and in alluvial deposits.
Gold is the most malleable of all metals; a single gram can be beaten into a sheet of 1 square meter, and an avoirdupois ounce into 300 square feet.
The most stable of these is The production of gold from a more common element, such as lead, has long been a subject of human inquiry, and the ancient and medieval discipline of alchemy often focused on it; however, the transmutation of the chemical elements did not become possible until the understanding of nuclear physics in the 20th century.
The first synthesis of gold was conducted by Japanese physicist Hantaro Nagaoka, who synthesized gold from mercury in 1924 by neutron bombardment.
Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as green gold.
Blue gold can be made by alloying with iron, and purple gold can be made by alloying with aluminium.
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.