English: The earliest evidence of goldworking in the Western Hemisphere dates to around 2000 BC, when gold was first hammered into thin foil sheets in ancient Peru. But it was the goldsmiths of Colombia who had access to the largest veins of gold ore, which they extracted by "placer mining" (panning) and by building simple, vertical shaft mines. Gold was melted and worked in a variety of techniques, including hammering, often around a wooden form, and lost-wax casting (in which a wax model of an object is made and encased in clay, which is fired, causing the wax to melt and run out through a hole; molten gold is then poured into the hole and hardens, and the resulting figure is revealed when the clay mold is broken apart). Much ancient American gold is naturally alloyed, or mixed, with copper, with percentages of copper rising to as high as 70 percent. This material, called "tumbaga," often has a reddish color. Ancient Colombian metalworkers developed "depletion gilding" techniques, in which the copper was removed from the gold using organic acids. The most famous Muisca artifacts are "tunjos," human images cast using the lost-wax technique and left much rougher in surface texture than most ancient Colombian gold. The knowledge of goldworking spread from the central and northern Andes into Central America, and gradually a blend of techniques and imagery developed into what is known as the "International Style." Very little of this material survived the Spanish conquest.