"Temperatures can be raised with energy released during exothermic... reactions. Copper and are commonly located in close proximity... A mixture of ... ...and ... ...heated to only to 700 °C ...automatically reaches a temperature, through a heat producing chemical reaction, that is close to that for extracting copper. The addition of a flux, which in Egypt was a native salt called (), lowered the fusion point sufficiently for copper extraction. Silver can be smelted similarly."