Electrum is a naturally occurring alloy of gold and silver,   with trace amounts of copper and other metals. Its color ranges from pale to bright yellow, depending on the proportions of gold and silver. It has been produced artificially, and is also known as "green gold". 
Electrum was used as early as the third millennium BC in Old Kingdom of Egypt, sometimes as an exterior coating to the pyramidions atop ancient Egyptian pyramids and obelisks. It was also used in the making of ancient drinking vessels. The first known metal coins made were of electrum, dating back to the end of the 7th century or the beginning of the 6th century BC. For several decades, the medals awarded with the Nobel Prize have been made of gold-plated green gold.
The name "electrum" is the Latinized form of the Greek word ἤλεκτρον (ḗlektron), mentioned in the Odyssey referring to a metallic substance consisting of gold alloyed with silver. The same word was also used for the substance amber, likely because of the pale yellow color of certain varieties.  It is from amber’s electrostatic properties that the modern English words "electron" and "electricity" are derived. Electrum was often referred to as "white gold" in ancient times, but could be more accurately described as "pale gold", as it is usually pale yellow or yellowish-white in color. The modern use of the term white gold usually concerns gold alloyed with any one or a combination of nickel, silver, platinum and palladium to produce a silver-colored gold.
Electrum consists primarily of gold and silver but is sometimes found with traces of platinum, copper, and other metals. The name is mostly applied informally to compositions between about 20–80% gold and 20–80% silver, but these are strictly called gold or silver depending on the dominant element. Analysis of the composition of electrum in ancient Greek coinage dating from about 600 BC shows that the gold content was about 55.5% in the coinage issued by Phocaea. In the early classical period, the gold content of electrum ranged from 46% in Phokaia to 43% in Mytilene. In later coinage from these areas, dating to 326 BC, the gold content averaged 40% to 41%. In the Hellenistic period, electrum coins with a regularly decreasing proportion of gold were issued by the Carthaginians. In the later Eastern Roman Empire controlled from Constantinople, the purity of the gold coinage was reduced, and an alloy that can be called electrum began to be used.
Electrum is mentioned in an account of an expedition sent by Pharaoh Sahure of the Fifth Dynasty of Egypt. It is also discussed by Pliny the Elder in his Naturalis Historia . Electrum is also mentioned in the Hebrew Scriptures, whose prophet Ezekiel is said to have had a vision of Jehovah on a celestial chariot (Ezekiel 1:4).
The earliest known electrum coins, Lydian and East Greek coins found under the Temple of Artemis at Ephesus, are currently dated to the last quarter of the 7th century BC (625–600 BC).  Electrum is believed to have been used in coins c. 600 BC in Lydia during the reign of Alyattes. 
Electrum was much better for coinage than gold, mostly because it was harder and more durable, but also because techniques for refining gold were not widespread at the time. The discrepancy between gold content of electrum from modern Western Anatolia (70–90%) and ancient Lydian coinage (45–55%) suggests that the Lydians had already solved the refining technology for silver and were adding refined silver to the local native electrum some decades before introducing the pure silver coins cited below. 
In Lydia, electrum was minted into coins weighing 4.7 grams (0.17 oz), each valued at 1⁄3 stater (meaning "standard"). Three of these coins—with a weight of about 14.1 grams (0.50 oz)—totaled one stater, about one month's pay for a soldier. To complement the stater, fractions were made: the trite (third), the hekte (sixth), and so forth, including 1⁄24 of a stater, and even down to 1⁄48 and 1⁄96 of a stater. The 1⁄96 stater was only about 0.14 grams (0.0049 oz) to 0.15 grams (0.0053 oz). Larger denominations, such as a one stater coin, were minted as well.
Because of variation in the composition of electrum, it was difficult to determine the exact worth of each coin. Widespread trading was hampered by this problem, as the intrinsic value of each electrum coin could not be easily determined.  The gold content of naturally occurring electrum in modern Western Anatolia ranges from 70% to 90%, in contrast to the 45–55% of gold in electrum used in ancient Lydian coinage of the same geographical area. This suggests that one reason for the invention of coinage in that area was to increase the profits from seigniorage by issuing currency with a lower gold content than the commonly circulating metal. (See also debasement).
These difficulties were eliminated circa 570 BC when the Croeseids, coins of pure gold and silver, were introduced.  However, electrum currency remained common until approximately 350 BC. The simplest reason for this was that, because of the gold content, one 14.1 gram stater was worth as much as ten 14.1 gram silver pieces.
Alyattes, sometimes described as Alyattes I, was the fourth king of the Mermnad dynasty in Lydia, the son of Sadyattes, grandson of Ardys, and great-grandson of Gyges. He died after a reign of 57 years and was succeeded by his son Croesus.
A coin is a small, usually round and flat, piece of metal or plastic used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in large quantities at a mint in order to facilitate trade. They are most often issued by a government. Coins often have images, numerals, or text on them. Obverse and its opposite, reverse, refer to the two flat faces of coins and medals. In this usage, obverse means the front face of the object and reverse means the back face. The obverse of a coin is commonly called heads, because it often depicts the head of a prominent person, and the reverse tails.
The denarius was the standard Roman silver coin from its introduction in the Second Punic War c. 211 BC to the reign of Gordian III, when it was gradually replaced by the antoninianus. It continued to be minted in very small quantities, likely for ceremonial purposes, until and through the Tetrarchy (293–313).
Lydia was an Iron Age kingdom of western Asia Minor located generally east of ancient Ionia in the modern western Turkish provinces of Uşak, Manisa and inland Izmir. The ethnic group inhabiting this kingdom are known as the Lydians, and their language, known as Lydian, was a member of the Anatolian branch of the Indo-European language family. The capital of Lydia was Sardis.
Croesus was the king of Lydia, who reigned from 585 BC until his defeat by the Persian king Cyrus the Great in 547 or 546 BC. According to Herodotus, he reigned 14 years.
Orichalcum or aurichalcum is a metal mentioned in several ancient writings, including the story of Atlantis in the Critias of Plato. Within the dialogue, Critias claims that orichalcum had been considered second only to gold in value and had been found and mined in many parts of Atlantis in ancient times, but that by Critias's own time orichalcum was known only by name.
The history of coins stretches back to the first millennium BC/BCE. Notable examples of coins include the Lydian Lion coins, Persian daric and siglos, Tong Bei, the dirham and gold dinar.
The history of ancient Greek coinage can be divided into four periods: the Archaic, the Classical, the Hellenistic and the Roman. The Archaic period extends from the introduction of coinage to the Greek world during the 7th century BC until the Persian Wars in about 480 BC. The Classical period then began, and lasted until the conquests of Alexander the Great in about 330 BC, which began the Hellenistic period, extending until the Roman absorption of the Greek world in the 1st century BC. The Greek cities continued to produce their own coins for several more centuries under Roman rule. The coins produced during this period are called Roman provincial coins or Greek Imperial Coins.
A mint is an industrial facility which manufactures coins that can be used as currency.
Pactolus, now named Sart Çayı, is a river near the Aegean coast of Turkey. The river rises from Mount Tmolus, flows through the ruins of the ancient city of Sardis, and empties into the Gediz River, the ancient Hermus. The Pactolus once contained electrum that was the basis of the economy of the ancient state of Lydia which used the naturally occurring alloy of gold and silver to forge the first coins under Alyattes of Lydia.
The stater was an ancient coin used in various regions of Greece. The term is also used for similar coins, imitating Greek staters, minted elsewhere in ancient Europe.
This glossary of numismatics is a list of definitions of terms and concepts relevant to numismatics and coin collecting, as well as sub-fields and related disciplines, with concise explanations for the beginner or professional.
The earliest coinage of Asia is also the oldest coinage of the world. Coins were invented several times independently of each other. The earliest coins from the Mediterranean region are from the kingdom of Lydia, and are now dated ca. 600 BCE. The dating of the earliest coins of China and India is difficult and the subject of debate. Nevertheless, the first coins of China are at least as old as the earliest Lydian coins and possibly older, while the earliest coins of India seems to have appeared at a later stage.
Silver coins are considered the oldest mass-produced form of coinage. Silver has been used as a coinage metal since the times of the Greeks; their silver drachmas were popular trade coins. The ancient Persians used silver coins between 612–330 BC. Before 1797, British pennies were made of silver.
The Achaemenid Empire issued coins from 520 BCE–450 BCE to 330 BCE. The Persian daric was the first gold coin which, along with a similar silver coin, the siglos represented the first bimetallic monetary standard. It seems that before the Persians issued their own coinage, a continuation of Lydian coinage under Persian rule is likely. Achaemenid coinage includes the official imperial issues, as well as coins issued by the Achaemenid provincial governors (satraps), such as those stationed in Asia Minor.
Group 11, by modern IUPAC numbering, is a group of chemical elements in the periodic table, consisting of copper (Cu), silver (Ag), and gold (Au), and roentgenium (Rg), although no chemical experiments have yet been carried out to confirm that roentgenium behaves like the heavier homologue to gold. Group 11 is also known as the coinage metals, due to their usage in minting coins—while the rise in metal prices mean that silver and gold are no longer used for circulating currency, remaining in use for bullion, copper remains a common metal in coins to date, either in the form of copper clad coinage or as part of the cupronickel alloy. They were most likely the first three elements discovered. Copper, silver, and gold all occur naturally in elemental form.
Billon is an alloy of a precious metal with a majority base metal content. It is used chiefly for making coins, medals, and token coins.
The coinage metals comprise, at a minimum, those metallic chemical elements which have historically been used as components in alloys used to mint coins. The term is not perfectly defined, however, since a number of metals have been used to make "demonstration coins" which have never been used to make monetized coins for any nation-state, but could be. Some of these elements would make excellent coins in theory, but their status as coin metals is not clear. In general, because of problems caused when coin metals are intrinsically valuable as commodities, there has been a trend in the 21st century toward use of coinage metals of only the least exotic and expensive types.
Hermodike II has been attributed with inventing coinage by Aristotle. Other historians have translated the name as Hermodice, Damodice or Demodike as translated by Julius Pollux.
The Croeseid, anciently Kroiseioi stateres, was a type of coin, either in gold or silver, which was minted in Sardis by the king of Lydia Croesus from around 550 BC. Croesus is credited with issuing the first true gold coins with a standardised purity for general circulation, and the world's first bimetallic monetary system.