Electrum

Electrum was a naturally occurring silver-gold alloy with half the value of pure gold: 1 electrum piece (ep) was worth worth 50 copper pieces (cp), 5 silver pieces (sp), 1/2 of a gold piece (gp), or 1/20 of a platinum piece (pp). Electrum was worth 25 gp per pound as a trade good.

Value and terminology
Most of Faerûn used "standard rates of exchange for coinage," based on the silver and gold standard, with 1 cp worth 1/100 gp, 1 sp worth 1/10 gp, 1 ep worth 1/2 gp, and 1 pp worth 10 gp.

A standard electrum coin was approximately 30.6 mm in diameter and weighed approximately 9 grams apiece (or 50 to one pound).

Electrum coins were called blue eyes, harmarks , or electrums in Sembia; thammarchs in Cormanthyr; blue eyes  in Cormyr; centaurs or decimes in Amn; centarches , tazos, or zonths in Calimport; moons in Waterdeep; and electrum moons in Silverymoon.

Throughout the Western Heartlands, most electrum coins from abroad were called blue eyes regardless of origin. Exceptions included:
 * The original shining blue crescent-shaped electrum moon of Silverymoon, a coin worth 1 ep throughout the Realms but twice that within the city itself.
 * The harbor moon of Waterdeep, a cresent shaped Waterdhavian coin made of platinum, inset with electrum, and punched with a central hole. It was used for bulk transactions, one coin being worth 50 gp within the city of Waterdeep and worth 2 gp –30 gp anywhere else.

"In lieu of platinum pieces, Sembia mints electrum pieces (ep) known as blue-eyes, each equal in value to 5 gp."

Other uses
The spell Khelben's warding whip used a pinch of powdered electrum as a material component.

The spell Leomund secret chest could use a chest fashioned from bronze, copper, or silver with fittings of electrum or silver.

Magical morning stars known as storm stars were crafted from electrum-plated steel. They could unleash a chain lightning effect.

An electrum mounting allowed witherite to be worn as a protection to necromantic attacks.

Two notable tomes—The Chambeeleon and The Tome of the Unicorn—had electrum pages, with the latter also having electrum covers.

If one of the twisted bands of a shoonring was made of electrum, this usually indicated that the ring contained multiple powers and enhanced the effects of the magics involved.

Conversion

 * AD&D (1st Ed.)
 * 200 cp = 20 sp = 2 ep = 1 gp = 1&frasl;5 pp
 * 100 cp = 10 sp = 1 ep = ½ gp = 1&frasl;10 pp


 * AD&D 2nd Ed.
 * 100 cp = 10 sp = 2 ep = 1 gp = 1&frasl;5 pp
 * &#8199;50 cp = &#8199;5 sp = 1 ep = ½ gp = 1&frasl;10 pp


 * D&D 3rd Ed.
 * 100 cp = 10 sp = 1 gp = 1&frasl;10 pp
 * Electrum is not mentioned in the core rules, and common electrum coins are not mentioned in the Forgotten Realms Campaign Setting.


 * D&D 4th Ed.
 * 100 cp = 10 sp = 1 gp = 1&frasl;100 pp = 1&frasl;10,000 ad
 * Electrum is not mentioned in the core rules, and only a Sembian electrum coin (worth 5 gp?) is mentioned in the Forgotten Realms Campaign Guide.


 * D&D 5th Ed.
 * 100 cp = 10 sp = 2 ep = 1 gp = 1&frasl;10 pp
 * &#8199;50 cp = &#8199;5 sp = 1 ep = ½ gp = 1&frasl;20 pp

Background
The word electrum comes form a Greek word meaning pale-yellow, used both for the alloy and for amber. Properties of amber led to to the modern English words electron and electricity.

Electrum alloys are primarily gold and silver (20–80% of each), with trace amounts of copper, platinum, and other metals. When used for Mediterranean coinage, the amount of gold (40–55%) was lower than local natural alloys (~70%) showing that the minters were adding silver to reduce the gold percentage. The color of electrum alloys (described as white gold, pale gold, or green gold) depended on the ratio of silver and gold (white- or pale-yellow) and trace elements such as copper (greenish-yellow).