Age of EmpiresGold Mines in Age of Empires are rare and the gold extracted from them is often crucial for victory. Mining gold is a quicker and often safer method of acquiring gold than trading. Gold Mines sometimes appear in groups and sometimes singly. If Coinage is researched, the productivity of a Gold Mine increases from 400 to 500.
Age of Empires IIGold Mines in Age of Empires II are more common than in the first game, and gold is more regularly used as a resource. As such, its value is reduced, although it is still quicker and more efficient to gather from a Gold Mine than trade with other players or through Relics.
Age of MythologyGold Mines in Age of Mythology are quite common and all human military units require gold to be produced. Any worker unit can mine gold from a Gold Mine, although Dwarves are the game's most efficient miners.
"Gold occurs in alluvial placers and natural deposits underground. Alluvial elemental gold could be gained by ancient civilizations by washing away the sand particles with water in pans or sieves and then melting the remaining bits of gold. Underground ore was extracted by hand, which required a great deal of manpower, often in the form of slaves. In Egypt, gold-containing quartz veins were heated, then chipped out with hammers and chisels. The quartz was then pulverized in mills and the metal extracted by washing. The gold produced by this method was between 17 and 23.5 carats in purity.
Gold was almost entirely decorative, as it was too weak for crafting functional items such as containers or armor."—In-game help section
Age of Empires III
"Fast but expiring source of Coin."—In-game description
Age of Empires III does not have gold as a resource, but instead has coin, an amalgam of all forms of wealth. In addition to Gold Mines, players can obtain coin from Silver Mines, Copper Mines, and Tin Mines (The Warchiefs). All of these are used up rather quickly.
"In 1848, the discovery of gold at Sutter's Mill in what would soon be California kicked off a gold rush that brought tens of thousands of hopeful prospectors across the wild frontiers of America. The influx of prospectors, whether they struck it rich or not, caused a boom in the economy focused on serving the needs of these prospectors. This further supported and reinforced the drive west with railroads and settlements. Sutter himself was a farmer who discovered a gold nugget in a river running through his land. He was ultimately ruined when his farmhands ran off to join the search for gold and his livestock were poached by squatters."