Metalworking oxidation is one of the main reasons that gold is found in nuggets. These nuggets are relatively pure gold and are workable as they are found. Copper ore, being relatively abundant, and tin ore became the next important players in the story of metalworking. Using heat to smelt copper from ore, a great deal of copper was produced. It was used for both jewelry and simple tools. However, copper by itself was too soft for tools requiring edges and stiffness. At some point tin was added into the molten copper and bronze was born. Bronze is an alloy of copper
2519 aluminium alloy 2519 aluminium alloy AA 2519 is an aluminium alloy principally containing copper (5.3–6.4%) as an alloying element. It also contains 0.25% silicon, 0.30% iron, 0.10–0.50% manganese, 0.05–0.40% magnesium, 0.10% zinc, 0.02–0.10% titanium, 0.05–0.15% vanadium, 0.10–0.25% zirconium, 0.40% silicon-iron compounds, and up to 0.15% trace elements. The density of 2519 aluminium is . It was first registered in 1985, in the United States. One application for this alloy is in aircraft armor, where it has equivalent ballistic characteristics to AA 7039, and a reduced susceptibility to stress corrosion cracking as compared to AA 5083. AA 2519-T87 plate is weldable using AA