The purity of gold is measured in carats. Pure gold is too soft in this state to be used effectively in jewellery. So it is alloyed with copper or other metals to increase its strength and durability. Common measurements once the alloy is added are 18 carat (75% gold), 14 carat (58.5%), and 9 carat (37.5%). A higher carat measurement in gold content indicates a greater value of the jewellry piece. Gold jewellery should always be stamped with the carat mark, either 750 (the marking for 18ct), 585 (the marking for 14ct), or 375 (the marking for 9ct). In addition, to assure its quality, the piece should also be stamped with the sponsor's or maker's mark and the mark of the Assay Office where the piece was authenticated if it weighs over 1g. Items under 1g in metal weight do not (legally) require hallmarking.
Yellow gold is the most common colour and is usually alloyed with silver and copper. Yellow and white gold are similar in strength and malleability, making them perfect for jewellery that is worn daily. White gold is alloyed with nickel, copper, and zinc--and while it looks similar to platinum, it has vastly different properties. Rose-coloured gold is alloyed with copper and is often used to accent white or yellow gold. The saturation of colour varies from piece to piece and according to gold content.
To keep gold shining and scratch-free, avoid contact with chlorine and other harsh chemicals. Do not wear jewellery during rough work and be sure to store it in a fabric-lined jewellery box or pouch. To clean gold jewellry, use warm water, a mild soap and a soft bristled brush, if needed.
Pure silver is soft and easily damaged. To give it more durability when creating jewellery, it is combined with copper, which makes it sterling silver. Sterling silver is 92.5% silver and 7.5% copper, but this alloy does not have an effect on the value of the metal. To ensure that the silver is high quality, the piece should be stamped with a purity mark (eg 925). In addition, to assure its quality, it should also be stamped with the sponsor's or maker's mark and the mark of the Assay Office where the piece was tested, if it weighs over 7.7g. Items under 7.7g in weight do not (legally) require hallmarking.
Silver should not come into contact with harsh household chemicals such as bleach, ammonia, or chlorine. To avoid scratches, store silver in a jewellery box or pouch. Silver tends to tarnish as it reacts with sulphur or hydrogen sulphide in the air. Cleaning and wearing it regularly will help maintain its shine and prevent this from happening. Immediately upon noticing discolouration, use a polish made specifically for removing tarnish and apply with a soft cloth.
Platinum is the most durable of fine jewellery metals. It does not chip or splinter easily, making it perfect for diamond and gemstone settings. It is similar in colour to white gold, but compared side by side, the difference is clear. Platinum jewellery is usually 90% pure platinum with 10% iridium or palladium alloy. To guarantee its quality, each piece should be stamped with a Hallmark.
Palladium joins gold, silver and platinum as the fourth recognised precious metal. It is one of the platinum group metals. Palladium is bright, white, tarnish resistant, and durable. The UK hallmark for palladium has now been made a legal requirement for all articles of the precious metal weighing more than 1 gram. Articles can be marked as containing a minimum of either 500, 950 or 999 parts per thousand of palladium.