While pure gold is yellow in colour, it can be changed into various colours. These colours are generally obtained by alloying gold with other elements in various proportions.
For example, alloys which are mixed 14 parts gold to 10 parts alloy create 14 carat gold. There are many possible alloys and mixtures, but in general the addition of silver will colour gold white, and the addition of copper will colour it red.
An alloy with a mix of around 50/50 copper and silver added to the gold, gives the range of yellow gold alloys the public is accustomed to seeing in the marketplace.
White gold is an alloy of gold and at least one white metal, usually nickel, manganese or palladium.
White gold alloys can be used for 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 mixed with other metals like copper, silver, and platinum for weight and durability.
White gold is usually plated with rhodium to provide its distinctive mirror finish. Many believe that the colour of the rhodium plating is actually the colour of white gold.
This plating can wear away, revealing the yellow-gray colour of the white gold. When this happens, your jeweller can have the piece replated in rhodium to restore the full brilliance of the piece.
Rose gold is a gold and copper alloy widely used for specialised jewellery. It is also known as pink gold and red gold.
Although the names are often used interchangeably, the difference between red, rose, and pink gold is the copper content – the higher the copper content, the stronger the red colouration.
Green gold alloys are made by leaving the copper out of the alloy mixture and just using gold and silver. It actually appears as a greenish yellow rather than green.
Stainless steel is a relatively hard and durable metal. It is similar in appearance to silver and will not tarnish which is why it is increasingly used in jewellery.
Pure gold has a bright yellow colour. Gold jewellery is usually described in terms of ‘caratage’ to indicate the level of the gold content. Gold is often mixed with other metals to increase its strength or change its colour. This mixture is called an alloy. Pure gold (24ct) is very soft and can show signs of wear easily. Most gold jewellery sold in South Africa is 9ct.
Many countries allow various caratages of gold jewellery to be sold. In South Africa one can sell 5, 8, 9, 10, 14, 18, 19.2, 20, 22 and 24 carat gold. The value of gold jewellery is based, in part, on its gold content. Consequently, most gold jewellery worldwide is marked with its caratage or fineness, often as part of the hallmark. You can recognise the gold content by the hallmark.
Carat of gold is expressed in parts of pure gold per 1000, as per the following examples:
• 750 fineness, the measure for 18ct gold indicates 750 parts of gold per 1000 or 75% gold;
• 375 fineness, the measure for 9ct gold indicates 375 parts of gold per 1000 or 37.5% gold.
New Metals for Jewellery
Stainless Steel Jewellery
Stainless jewellery can be (but is not always) made without nickel making it suitable for those allergic to nickel.
Stainless steel jewellery does not have the same lustre or shine as other metals but some prefer its slightly more metallic appearance, particularly men.
Titanium is a natural element which has a silver-greyish-white colour. Titanium is the hardest natural metal in the world. It is very strong, three times the strength of steel and much stronger than gold, silver and platinum and yet is very light in weight. Pure titanium is also 100% hypoallergenic which means it will not react to your skin.
Titanium provides several unique factors that make it the ideal metal for jewellery rings. It offers an exotic array of colours such as blue, purple, blue-moon, night sky and black rainbow colours. The colour is created by oxidisation. The colour will not fade or chip though it can be scratched off.
Palladium is a rare and lustrous silvery-white metal that resembles platinum and forms part of the platinum group metals along with platinum, rhodium, ruthenium, iridium and osmium.
Palladium is used as a precious metal in jewellery as an alternative to platinum or white gold. This is due to its naturally white properties, eliminating the need for rhodium plating. It is proportionally much lighter than platinum.
Platinum is one of the rarest of the precious metals. Naturally white, platinum will not fade or tarnish – keeping its natural white colour forever. Platinum is also a very strong metal. Its purity makes it hypo-allergenic and ideal for those with sensitive skin. Similar to gold, the purity of the metal is expressed in parts per 1000 and can be identified through its hallmark.
In South Africa manufacturers and retailers are required to ensure that the jewellery is marked with one of the following: Platinum, Pt, Pt950, Plat, Plat 950. The standard in South Africa for all platinum jewellery is 95% purity. South Africa is the leading producer.
What is the difference between platinum and white gold?
Platinum is naturally white, whereas gold is yellow. White gold is a mixture of yellow gold with other metals, often one of the platinum group metals to achieve a white look. The colour of white gold is further enhanced with rhodium plating, another platinum group metal.
Why is a platinum ring more expensive than gold?
The rarity of platinum means that its price is invariably higher than that of gold. Platinum jewellery is generally 95% pure platinum compared with 18 carat gold jewellery which is 75% gold.
Platinum is denser than gold, so a piece of platinum jewellery weighs over a third more than the same piece made of 18 carat gold.
Will platinum jewellery scratch?
All precious metals can scratch, and platinum is no exception. However, a scratch on platinum is merely a displacement of the metal and none of its volume or value is lost.
Silver is a soft, white, lustrous metal and is used in currency, ornaments and jewellery. Sterling silver is an alloy of silver containing 92.5% pure silver and 7.5% other metals, usually copper.