Colored gold

Colored gold is the name given to any gold that has been treated using techniques to change its natural color. Pure gold is slightly reddish yellow in color, but colored gold can come in a variety of different colors by alloying it with different elements. Colored golds can be classified in three groups: Alloys with silver and copper in various proportions, producing white, yellow, green and red golds. These are typically malleable alloys. Intermetallic compounds, producing blue and purple golds, as well as other colors. These are typically brittle, but can be used as gems and inlays. Surface treatments, such as oxide layers. Pure 100% (in practice, 99.9% or better) gold is 24 karat by definition, so all colored golds are less pure than this, commonly 18K (75%), 14K (58.5%), 10K (41.6%), or 9K (37.5%). White gold is an alloy of gold and at least one white metal (usually nickel, silver, or palladium). Like yellow gold, the purity of white gold is given in karats. White gold's properties vary depending on the metals used and their proportions. As a result, white gold alloys can be used for many different purposes: while a nickel alloy is hard and strong, and therefore good for rings and pins; gold–palladium alloys are soft, pliable, and good for white-gold gemstone settings, sometimes with other metals, like copper, silver, and platinum, added for weight and durability (although this often requires specialized goldsmiths). The term white gold is used very loosely in the industry to describe karat gold alloys with a whitish hue. The word white covers a broad range of colors that borders or overlaps pale yellow, tinted brown, and even very pale rose. The jewelry industry often conceals these off-white colors by rhodium plating; thus it is a common misconception that the color of the rhodium plating, which is seen on many commercial pieces, is the actual color of white gold. A common white gold formulation consists of 90% wt. gold and 10% wt. nickel. Copper can be added to increase malleability.