Karats is a measurement of the content of gold. Not to be confused with Carat (Ct) which is the unit of weight measurement for gemstones.
The most common karat gold used in Australia is 18K, 14K and 9K. 18K is more expensive than 14K and 9K as it has a higher gold content. Jewellery is rarely made from pure 24K gold as it is too expensive and it is too soft and therefore wears out faster and is easy to bend out of shape.
- 9K gold contains 37.5% pure gold (375 parts per thousand parts)
- 14K gold contains 58.5% pure gold (585 parts per thousand parts)
- 18K gold contains 75% pure gold (750 parts per thousand parts)
Karat gold is normally stamped to indicate with, for example, 9K gold would either be stamped 9K or 375, 18K gold would be stamped either 18K or 750.
Gold Plated Jewellery (GEP or GP)
Gold plated jewellery is jewellery that has a layer of gold applied to a base metal by an electrolytic process. This gives a look similar to karat gold. Gold plated jewellery is a cheap alternative and will wear off after time.
The most common gold colour is yellow gold, followed by white gold and rose gold. The colour of the gold doesn’t make a difference to the gold content (karat rating). The gold is mixed with different metals to achieve different colours.
- Yellow gold can vary in colour. 18K yellow gold will have a brighter yellow colour compared to 9K gold.
- Rose gold is achieved normally by mixing pure gold with other metals such as copper into it.
- White gold is made by mixing pure gold with metals such as silver and palladium. It is often coated with a metal named “rhodium”. The rhodium gives jewellery a really white appearance. White gold jewellery normally needs to re-rhodium coated every 12-18 months. Ask your local jeweller.
When comparing metals of the same karat, white gold tends to be a little more expensive.
Normally gold rarely tarnish or corrode however gold can sometimes leave a black mark on your skin under the following conditions.
- Being contacted in perspiration containing certain chemicals which react with the molecules of other metals in the gold alloy. This can happen when changes occur in body chemistry, for example pregnancy or while on medication.
- Being contacted in cosmetics, hairsprays and perfumes
- Being exposed to air pollutants from industry
- The least likely cause may be an allergy to gold or one of the other metals in the alloy, such as nickel, which is commonly used in fashion jewellery and in some white gold.
Sterling Silver is a mixture or alloy of silver and other metals, usually copper, to give it strength. Sterling silver contains at least 92.5% silver and is usually stamped with the word “Sterling” or .925.
Causes of Tarnishing
Several reasons why silver may eventually lose its sheen are:
- being in ocean or chlorine in swimming pools
- being in contact with perspiration
- being in contact with perfume, soap or hairspray
Most of our silver jewellery are Rhodium plated. Rhodium is a semi-precious metal that lends a White gold or platinum look to sterling silver jewellery. Rhodium plated silver doesn’t normally tarnish.