ABSTRACT
Gold is a comparatively rare native metallic element, ranking fiftieth in abundance in the earth’s crust. The chemical symbol for gold is Au, from the Latin aurum for gold. Metallic gold is an exceptionally stable form of the element and most deposits occur in this form. The main elements with which gold is admixed in nature include silver, tellurium, copper, nickel, iron, bismuth, mercury, palladium, platinum, indium, osmium, iridium, ruthenium, and rhodium. The native gold-silver alloys have a color range from pale yellow to pure white, depending on the amount of silver present. Finely divided gold is black, like most other metallic powders, while colloidally suspended gold varies in color from deep ruby red to purple. Gold occurs as metallic gold (Au0) and also as Au+ and Au+3, so that it occurs in combination with tellurium as calaverite (AuTe2) and sylvanite (AuAgTe4), and also with tellurium, lead, antimony, and sulfur as nagyagite, Pb5Au(Te,Sb)4S5-8 (Rose 1948; Ransom 1975; Sadler 1976; Puddephatt 1978; Krause 1996).
