If you're in search of interesting and unusual jewellry to add to your wardrobe, take another look at gold. While yellow, white, and rose gold are common inhabitants of most jewellry stores, now you can also find additional colors suitable for matching with different outfits or even just your mood. Here are four extra gold colors to look out for the next time you visit a jeweller's shop.

Blue Gold

Blue gold is available as both a surface alloy and a whole-piece alloy. One surface alloy mixes gold with iron and nickel, and this is used as a coating on top of other gold. Another version plates regular gold with an additional layer of gold plus a second layer of a material called indium. You can also find whole alloys of blue gold that are made form an alloy of gold and gallium, though these are not going to have a vivid blue color.

Green Gold

This is actually not a new substance, and it's more yellow-green than bright green. This is a mix of gold and silver that can actually be found naturally, though for jewellry purposes it's usually manufactured. You're not likely to find pieces made solely of green gold because it is so soft, but you can find jewellry with decorative elements made from green gold.

Purple Gold

A gold and aluminum mix that is also used as an added decorative element on top of other jewellry, though in this case it's because the alloy is too hard and thus breaks easily. You'll often see purple gold called amethyst gold.

Black Gold

Black gold is an interesting phenomenon. It's formed in a few different ways with different materials. For example, you can have straight plating of regular gold with ruthenium or rhodium. You can also have regular gold where the surface has undergone oxidation with cobalt, for example. If oxidation sounds familiar, that's the process in which rust forms on iron after contact with water. Black gold isn't rough, and the oxidation is monitored, but that comparison gives you a better idea of how the black layer is organically formed on top of the gold.

If you have questions about finding different colors of gold jewellry, talk to a jeweller who works closely with goldsmiths or who creates his or her own designs. As people decide they want to see more variety in jewellry while still retaining the inherent gold value, you'll see more of these colors appear on the market. Contact a local company,like Highglow Jewellers Ltd jewellery, for more help.