There are many types of gold available. What you need to know before making a better informed decision when purchasing your next fine piece of jewellery.
Gold is considered a soft metal so pure gold jewellery would be too soft for everyday use. Therefore gold is mixed with other metals which can include silver, tin, nickel, zinc, palladium to make it harder and more durable. Karats (K) is the measurement of the purity of the 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 9K and 18K. 9K gold which contains 9 parts pure gold and 15 parts mixed metals. 18K gold contains 18 parts pure gold and 6 parts mixed metals. Calculated as a percentage, 9K gold contains 37.5% pure gold and 18K gold contains 75% pure gold, making 18K more expensive than 9K. The hardness of 18K gold and 9K gold is virtually the same. Pure gold is one of the least reactive elements. 9K gold being mixed with a higher percentage of other elements tends to be less resistant to exposure to chemicals in cleaning products, chlorine in pools and even perspiration can lead to your 9K gold jewellery looking a little dull and discoloured.18K gold has twice the amount of gold of 9K making it wear a little better over the years. 9K gold can be a great choice for dress rings, earrings and pendants that are not worn every day. For your engagement or wedding bands 18K gold is much more durable and longer lasting.
Gold is also mixed with other metals to produce different coloured golds. The most common gold colours are yellow gold, white gold and rose gold. Yellow gold can vary in colour. 18K yellow gold will have a brighter yellow colour compared to 9K yellow gold. Rose gold is achieved by mixing pure gold with other metals such as copper. White gold is made by combining pure gold with metals such as silver and palladium. It is also often plated with rhodium a type of metal that gives the piece of jewellery the white appearance. White gold jewellery may need to be re-rhodium coated once the existing rhodium coat wears away. When comparing gold metals of the same karat, white gold tends to be a little bit more expensive.
Gold plated jewellery. This is where a layer of gold is applied to a base metal by an electrolytic process. The gold plating can wear off over time.
Gold filled also known as gold overlay jewellery, is a solid layer of gold bonded with heat and pressure to a base metal. This layer can be 50-100,000 times thicker than gold plated jewellery.
Karat gold jewellery is normally stamped to identify the content of gold used. 9K gold would be stamped 9K or 375. 18K gold is stamped either 18K or 750.How to test if its real gold. Your local jewellery store would be the most reliable way to test if your gold jewellery is real. Please note the following advice is of a general nature. If you wanted to test it yourself an electronic gold tester could be used. This involves clipping the piece of jewellery to the tester and placing it an acid which will then tell you the purity of gold used. Another method is using a gold testing stone. You will need to rub the jewellery on the stone which will leave tiny fragments of gold. Then rub a gold test needle onto the stone near the gold sample. You then need to apply the appropriate acid and if its gold it will dissolve. You could also file into the jewellery and apply an appropriate acid. The gold will react to the acid to determine whether it is genuine. If you were to test for gold yourself make sure you read the instructions thoroughly of the test kit you are using before attempting any of these tests.