GOLD
Because of the softness of pure (24k) gold, it is 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 found in antique and Russian jewelry and has a distinct, though not dominant,
copper cast, creating rose gold. Blue gold can be made by alloying with iron and purple gold can be made by alloying with aluminium, although rarely done exceptin specialized jewelry.
Fourteen and eighteen carat gold alloys with silver alone appear greenish-yellow and are referred to as green gold.
White gold alloys can be made with palladium or nickel.Alternative white gold alloys are available based on palladium, silver and other white metals , but the palladium alloys are more expensive than those using nickel.
