9ct Gold is only about 27% or 28% Gold, what metals make up the other 72/73%?

Answer 1

Percentages by Weight

9 Carat Yellow - Gold 37.5%, Silver 10%, Copper 45%, Zinc 7.5%, Nickel 0%, Palladium 0%

9 Carat White - Gold 37.8%, Silver 0%, Copper 40%, Zinc 10.4%, Nickel 11.8%, Palladium 0%

Answer 2

As usual, the answer to a simple question is not always simple.
First, there are many different combinations of metals which can be used to make gold alloys. There are many different "recipes" for both 9 carat and 18 carat gold alloys. A carat simple means 1/24th, i.e. one part in 24. So 9 carat gold must be at least 9 parts gold out of 24, which is equivalent to 37.5%, the other 62.5% can be any other metal, the commonest used being copper and silver, but nickel, palladium, zinc, and other metals are used. Similarly with 18 carat gold, which has to be 18/24, equivalent to 75% gold, the rest being composed of any other metal. You would be quite correct to guess that each different "recipe" has its own different characteristics including hardness. It is quite possible to make hard or soft "recipes" for 9 carat and also for 18 carat and other gold alloys. In general, most common 18 carat gold alloys are both harder, and harder wearing than their 9 carat equivalent.

Answer 3

Pure gold is too soft for ordinary use and is hardened by alloying with silver, copper, and other metals. Gold and its many alloys are most often used in jewelry, coinage and as a standard for monetary exchange in various countries. When selling it in the form of jewelry, gold is measured in carats (k), with pure gold being 24k. However, it is more commonly sold in lower measurements of 22k, 18k, 14k and 10k. A lower "k" indicates a higher percent of copper or silver mixed into the alloy, with copper being the more commonly used metal between the two. Fourteen carat gold-copper alloy is nearly identical in color to certain bronze alloys, and both may be used to produce police and other badges. Eighteen carat gold with a high copper content is found in some antique jewelry and has a distinct, though not dominant copper cast, giving an attractively warm color. A similar carat weight when alloyed with silvery metals appears less warm in color, and some low karat white metal alloys are sold as "white gold", silvery in appearance with a sightly yellow cast but far more resistant to corrosion than silver or sterling silver. Carat weights of twenty and higher are more common in modern jewelry. Because of its high electrical conductivity and resistance to corrosion and other desirable combinations of physical and chemical properties, gold has emerged in the late 20th century as an essential industrial metal, particularly as a thin plating on printed circuit board contacts and electrical connectors.

The karat system is increasingly being complemented or superseded by the millesimal fineness system in which the purity of precious metals is denoted by parts per thousand of pure metal in the alloy.

The most common carats used for gold in bullion, jewelery making and goldsmithing are:
24 karat (millesimal fineness 999)
22 karat (millesimal fineness 916)
20 karat (millesimal fineness 833)
18 karat (millesimal fineness 750)
15 karat (millesimal fineness 625)
14 karat (millesimal fineness 585)
10 karat (millesimal fineness 417)
9 karat (millesimal fineness 375)

Answer 4

Often it is gold plating over a core of copper and nickel. The copper gives it a redish color and the nickel gives it strength and weight.

Adding copper yields a redder metal, iron blue, aluminium purple, platinum metals white, and natural bismuth together with silver alloys produce black.

Answer 5

because gold is non reactive it can pretty much be alloyed with anything, usually zinc, tin, iron or such other common metals or other impurities

Answer 6

Pure (24 carat) gold is a deep yellow colour (an orange shade of yellow) and is soft and very malleable. The coloured carat gold alloys range in gold content from 8 to 22 carats (33.3% - 91.6% gold) and can be obtained in a range of colour shades: green (actually a green shade of yellow), pale yellow, yellow, deep yellow, pink/rose and red. There are also white golds and even unusual coloured golds such as 'purple gold'. They all have different mechanical properties such as strength, hardness and malleability (ductility) and some alloys can be heat treated to maximise strength and hardness. There are gold alloys that are optimised for different manufacturing routes such as lost wax (investment) casting and stamping.

Almost all conventional, coloured carat golds are based on gold-silver-copper alloys, often with minor alloying additions. All three metals have the same crystal structure (face centred cubic, FCC) and so are compatible with each other over a large range of compositions. Typical minor additions include deoxidisers such as zinc and silicon, grain refiners such as iridium and cobalt and possibly metals such as nickel to strengthen the alloy. Larger zinc additions (about 1-2%) can improve melt fluidity and hence 'castability' in lost wax casting, as can silicon, resulting in better filling of the mould and better reproduction of surface detail. Even larger zinc additions (up to 10%) can improve malleability of certain carat golds, particularly 14 carat and lower, used for making jewellery by stamping from sheet. Additions of low melting point metals such as zinc, tin, cadmium and indium lower melting ranges and hence are used to make carat gold solders.

Gold is yellow and copper is red, the only two coloured pure metals. All other metals are white or grey in colour. The addition of a red colour to yellow, as every school child knows, makes the yellow pinker and eventually red. The addition of a white makes the yellow colour paler and eventually white. This principle of mixing colours is the same in carat golds. Adding copper to gold makes it redder and adding silver, zinc and any other metal makes gold paler. Thus, we can understand that lower carat golds, because we can add more alloying metals, can have a wider range of colours than the higher carat golds.

Thus at 22 carat (91.6% gold), we can only add a maximum of 8.4% of alloying metals and hence can only obtain yellow to pink/rose shades.

At 18 carat (75.0% gold) and lower, we can add 25% or more alloying metals and hence get colours ranging from green through yellow to red, depending on the copper: silver plus zinc ratio.

Good 9 ct white gold is 35.7% gold, and 62.5% silver in content. Cheaper white golds use other metals, other than silver.

Good 18 ct white gold and 14 ct white gold does not exsist! most fine jewlers will use Platinum for this in more expensive rings and ear-rings

Apart from copper, all other alloying metals to gold will tend to whiten the colour and so it is possible to make carat golds that are white in colour. White golds for jewellery were developed in the 1920's as a substitute for platinum.

Additions of any white metal to gold will tend to bleach it's colour. In practice, nickel and palladium (and platinum) are strong 'bleachers ' of gold ; silver and zinc are moderate bleachers and all others are moderate to weak in effect.

This has given rise to 2 basic classes of white golds - the Nickel whites and the Palladium whites. At the 9 carat (37.5% gold) level, a gold-silver alloy is quite white, ductile although soft and is used for jewellery purposes. White golds are available up to 21 carat.

Nickel alloying additions form hard and strong white golds up to 18 carat. They are difficult to work and suffer from socalled 'firecracking'. Most commercial alloys are based on gold-nickel-silver-zinc alloys with copper often added to improve malleability. This copper addition, of course, affects colour, and so such white gold alloys are not a good white colour - more a slight yellow/ brown tint, particularly if nickel content is also low. As a consequence, such white gold jewellery is normally electroplated with rhodium (a platinum metal) which is tarnish resistant and imparts a good white colour.

Unfortunately, many people, the female population especially, are allergic to nickel in contact with the skin and this gives rise to a red skin rash or irritation. The European Union countries have enacted legislation valid from the 20th January 2000 that limits nickel release from jewellery. Thus, in Europe, nickel white golds are being phased out and being replaced by palladium white golds. The USA is taking a more relaxed approach, requiring jewellery to be labelled as nickel-containing, and much jewellery in the West is now advertised as 'non-allergenic' or 'nickel-free'.

Additions of about 10 -12% palladium to gold impart a good white colour. But palladium is an expensive metal, dearer than gold and it is also a heavy metal. Thus jewellery in such palladium white golds will be more expensive than identical pieces in nickel whites for 2 reasons: firstly, the cost of the palladium and secondly, the impact of density - palladium white golds are denser and so such jewellery will be heavier and also contain more gold. It is also more difficult to process as the melting temperatures are substantially higher.

Many commercial palladium white golds only contain about 6-8% palladium plus silver, zinc and copper. Some may even contain some nickel [so a palladium white gold is not necessarily nickel-free]. These may also have less than a good white colour and so may also be rhodium plated.

Palladium white golds tend to be softer and more ductile compared to nickel whites and so will not wear as well. They are available in all caratages up to 21 carat. It is not possible to have a 22 ct white gold, for example.

In the European Union especially, there is a demand for cheaper alternatives to white golds than the palladium whites which are nickel-free. Many new alloys are coming to market, most of which rely on manganese additions as the main whitener. Some are palladium-free and others are low palladium alloys. Chromium and iron are also be used as whiteners. They tend to be hard and more difficult to process. Many of these alloys are not a good white colour, requiring rhodium plating, and many suffer cracking problems and tarnishing.

Answer 7

could be anything...my guess..zinc.