This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
This "king of metals," as it was formerly termed, is found native in the "veins" of rocks, and as gold-dust or nuggets in the sands of certain plains and rivers; it is separated by washing, or by means of mercury, which is afterward driven off by heat; it occurs also in alloy with silver, copper, and iron, but not as an oxide, nor in any other than the metallic form.
When pure it is of yellow color, having a tinge of green by reflected light, and is decidedly greenish when liquefied; it is of great density (sp. gr. 19.5), and is remarkably malleable, 280,000 thin leaves making only one inch in thickness. It is less easily oxidized than any other metal, and will not combine with oxygen by direct action, only through the medium of another oxide: thus the protoxide of gold is prepared by adding solution of potash to one of protochloride; it precipitates as a green powder. Gold combines also with chlorine and iodine, not with nitrogen or hydrogen. It is soluble only in a mixture of nitric with hydrochloric acid (aqua regia).