Gold has a characteristic yellow colour, which is, however, notably affected by small quantities of other metals; thus the tint is sensibly lowered by small quantities of silver, and heightened by copper. Gold has long served an important role in society as a form of currency. The price of gold has been an issue of great international importance. It has been the source of conflicts, military expeditions and speculation. In the 21st Century, gold has declined from its status as the basis of a nation''s currency and national gold reserves have been drawn down. Even with these changes gold retains a position in financial centres in addition to being an important commodity with a wide range of applications.
Gold is a good conductor of electricity, and is used in electrical contacts. While precious metals as a percentage of the total weight of E-waste are relatively small, the concentration of such gold, is much higher than is found in naturally occurring mineral ore.