Because of the softness of pure (24k) gold, usually alloyed with base metals for use in jewelry, altering its hardness and ductility, melting point, color and other properties. Alloys with lower caratage, typically 22k, 18k, 14k or 10k, contain higher percentages of copper, or other base metals or silver or palladium in the alloy. Copper is the most commonly used base metal, yielding a redder color. Eighteen-carat gold containing 25% copper is in antique and Russian jeweler. It has a distinct, though not dominant, copper cast, creating rose gold. Fourteen-carat gold-copper alloy is nearly identical in color to certain bronze alloys, and both used to produce police and other badges. Blue gold can be made by alloying with iron and purple gold can be made by alloying with aluminum, although rarely done except in specialize jewelry. Blue gold is more brittle and therefore more difficult to work with when making jewelry. Fourteen and eighteen carat gold alloys with silver alone appear greenish-yellow and referred to as green gold. White gold alloys made with palladium or nickel. White 18 carat gold containing 17.3% nickel, 5.5% zinc and 2.2% copper is silver in appearance. Nickel is toxic, however, and its release from nickel white gold controlled by legislation in Europe. Alternative white gold alloys are available based on palladium, silver and other white metals (World Gold Council), but the palladium alloys are more expensive than those using nickel. High-carat white gold alloys are far more resistant to corrosion than are either pure silver or sterling silver. The Japanese craft of Mokume-gane exploits the color contrasts between laminated colored gold alloys to produce decorative wood-grain effects.

Rings

A finger ring is a circular band worn as a type of ornamental jewelry around a finger; it is the most common current meaning of the word ring. Other types of metal bands worn as ornaments called rings, such as arm rings and neck rings. Rings worn by both men and women and can be of any quality. Various ring shapes and styles exist. The following are but a few. Flat wedding bands are the simplest form of ring. A flat wedding band consists of a strip of metal bent around into a loop and joined where the ends meet. Half-round rings, also called D-shape rings, are flat wedding bands filed half-round on the outside. Sleeve rings are rings that consist of a thin inner ring or sleeve, with several other rings stacked onto it to form one solid ring. Either the rings soldered onto the sleeve or the ends of the sleeve can be upset to keep them all together. A little of both can also be done. Solitaire rings are rings with a single large stone as a centerpiece, usually a diamond. Eternity rings are rings with stones, usually diamonds, of the same cut and size, set in one row all around the ring. The stones are usually round or square, and the setting is usually either claws or a channel setting. When the stones do not continue around the entire ring, but stop halfway around the finger, it is a half-eternity ring. Trinity rings or Trilogy Rings are three rings worn at one time. Cluster rings are rings with a group of stones in a cluster setting, forming the focal point of the ring. The cluster setting usually consists of one large stone in the center surrounded with several smaller stones. Tension Rings are a type of ring in which a single gemstone is held in place by pressure rather than prongs, a bezel or other mounting. The metal setting is actually spring-loaded to exert pressure onto the gemstone. In the United States and Canada, ring sizes specified using a numerical scale, with quarter and half sizes. An increase of a full size is an increase of 0.032 inch in diameter, or roughly 1/10 inch in inside circumference. Generally, sizes in quarters and halves will not relate conventionally to anything on any known ruler. On one finger alone, a person may vary more than a whole ring size- depending on time of day, work performed, and other swelling-inducing activities/conditions. Therefore, in most cases quarter-sizes are meaningless unless one needs precise accuracy with a particular ring.