Among the industries found in colonial America, the production of plates, tankards, pitchers, flatware, and serving vessels fashioned from pewter was the trade provided to colonial households by pewtersmiths. Pewter is an alloy of two metals, tin and lead. America possessed rich deposits of the mineral galena, the ore from which lead is extracted, but it had no deposits of cassiterite, the ore of tin, which is commonly available in England. American pewterers required access to large quantities of these raw materials to successfully establish their industry in America. However, only finished products were to be sold to the colonies and the export of tin ore was forbidden. The English monarchy tightly controlled the export of goods and materials to the colonies through the establishment of export laws. Exactly which pewter goods were to be exported was largely controlled by the English pewter guilds. These measures ensured the English guilds a market in the New World for their goods, and significantly restricted the ability of American pewter smiths to compete. Without a source of cassiterite ore, American pewterers had to find another source of tin metal. The manufacture of pewter goods in England was a guild-controlled process; this meant that all pewter goods imported from England maintained a consistent level of quality. The amount of tin and lead present in the millions of pewterware pieces already in the colonies could therefore be accurately determined. Moreover, due to the low melting point of pewter metal, it could easily be melted down and re-cast into new forms with little loss of material. American pewtersmiths had only one course of action: to collect damaged or disused pewter goods and recycle them. One common colonial practice among pewterers was to offer one pound of new pewterware in exchange for three pounds of old. Subsequently, pewterers traveled from door to door, and sometimes town to town, in order to collect damaged vessels for repair or for recycling.