First of all there is a process that involves recovering gold metal from gold ore and converting it to pure gold, free from impurities (refining). It can be accomplished by electrolyte process, chemical treatment, smelting or other common refining methods. Large gold bars (ingots, gold bullion) are made by pouring the molten metal into molds (in a large holding crucible). During pouring it is positioned on a balance. When the balance records the required weight of gold, the pouring ceases. The standard gold bar held as gold reserves by central banks and such is the 400-troy-ounce (12.4-kilogram). The kilobar, which is 1,000 grams (32.15 troy ounces) in mass, and a 100 troy ounce gold bar are the bars that are more manageable and are used extensively for trading and investment. Smaller bars may be manufactured by minting or stamping from appropriately rolled gold sheets.