Gold Purity Chart
Chemical symbol for Gold = AU
This Handy Chart featured in the picture allows quick calculation of the pure gold content contained in fine jewellery using the stamp. It is Great for comparing value and assessing quality in precious metals. To use the chart first remember that pure gold is 24ct, which is also 24 parts per 24 pieces of Gold or 100 percent Gold and the amount of fine gold is expressed in number of Carats per 24. The fineness scale gives the gold content in parts per thousand and ranges from 0 to 1000.
Example calculation: 18ct gold is 18 parts per 24. Therefore 18 Divide 24 gives 0.75 shown as 75% Gold. This can also be shown as 75% of 1000 parts which is 750, the stamp for 18ct.
What is a precious metal?
Many metals are rare and precious however fine jewellery is primarily concerned with the noble metals. Noble metals are found in their natural state and are valued for their properties including resistance to tarnish with important hypoallergenic properties. These metals are readily workable, recyclable and can produce a brilliant lasting shine. Alloying together with other metals creates interesting new products with different colours and properties. The versatility and rarity of these metals are in high demand attracting a correspondingly high price.
Why is Gold Mixed?
Metals that are mixed together increasing their individual properties for a given application are known as Alloys. In the case of precious metals they are mixed with each other with small amounts of select metals to, improve their workability and colour. This can include adding Copper to improve strength and resistance to bending or wear from abrasion. Other metals such as Palladium can be added in the production of White Gold.
Common Gold Alloys
22ct Rich coloured Gold often worn in Middle eastern and Asian countries. The high Gold content enhances individual pieces tradeability and therefore is viewed as a personal store of wealth. The pieces are often sold by the gram with a low value put on the manufacturing.
Pro: High resistance to tarnish with excellent brightness in especially in hand cut details inscribed with a sharp tool. Excellent finish on intricate handmade filigree designs owing to the low oxidisation allowing many soldering operations to be performed.
Con: The rich yellow colour is not popular in western cultures and the metal can be considered a little too soft, easily bending with everyday use.
18ct Seventy Five percent pure Gold according to the formula above displaying a rich yellow colour with a higher proportion of alloys to strengthen the metal. The alloy is a blend of Copper and Silver combining to make one of the most beautiful colour mixtures amongst the yellow metals with an intoxicating luminescence. The 750 Alloy is available in White Gold, Rose Gold, Green Gold and Yellow Gold with these colours having further variations in shade according to the alloy used.
Pro: The best overall balance for colour, durability and intrinsic gold value. Excellent tarnish resistance and workability for a long lasting piece
Con: Can wear quicker than lower carat alloys and is more expensive at the initial time of purchase owing to the 75% gold content.
15ct Older blend often seen in jewellery made in the early Twentieth century although relatively uncommon in todays market. Many examples exhibit a distinctive Rose Gold type colour potentially because that type of blend was the aesthetic preference in that era.
Pro: contains no discernable benefit other than being the next used high carat metal below 18ct.
Con: Can be hard to match the colour of the metal for repairs and resizing or to create something to complement the original piece.
14ct Common European alloy with a Gold content of 58.5% stamped in the fineness scale as 585. Interestingly 14 divide 24 gives 0.583 so technically 14ct could be only 583 parts Gold. A high strenth alloy that makes a good high carat economy option with a slightly paler colour than 18ct yellow and virtually indistinguishable in The white Gold alloy. The Rose alloy is a common colour known Red Gold in Eastern Europe.
Pro: 14ct Alloy is very resistant to bending make it one of the strongest alloys however the colour is not to every users taste.
Con: Some alloys of 14ct can be too hard and crack, this hardening can happen from working the metal or when melting and reusing.
10ct Best of the Low Gold content alloys and recognised in the United States as the minimum acceptable standard for an item described as Gold. It is a useful choice for making chain and large heavy pieces that may be subject to increased wear. Heavy Bangles and Mens rings can benefit from the improved durability of this Alloy.
Pro: Universally accepted as a Gold Alloy by name thereby keeping value in the marketplace. Hard wearing alloy with a good consistent colour.
Con: Less common in Australia and potentially the same situation occurs in other countries making repairs and colour matching slightly more expensive.
9ct The lowest Carat alloy you will likely encounter but there are some lower alloys. There exists 7ct and 8ct alloys in the market however they are genrally not considered Gold products. The Formula chart above will work to help you determine the Gold content contained in these products. Available in all the colours however the White Gold alloy is extremely soft due to the higher silver content.
Pro: A very long lasting and hard wearing alloy with good colour and workability.
Excellent for Pendant bales and clasps where high wear is expected.
Con: May not be considered a proper Gold in some countries leading to disappointment. The high copper content can be more susceptible to chemical attack from skin acids and packaging materials . This copper can be eaten away by these chemicals leaving a brittle frosty coloured Gold alloy behind. The copper content can also cause rashes and skin irritation in some users.
Gold wear is serious Business
There are a multitude of diffent alloys used in precious Gold jewellery. The basic explanations above are a small part of the story with many more complications surrounding Alloys for Jewellers to consider. Gold wear occurs from the metal surface coming into contact with other surfaces causing a small amount of metal to be rubbed off. Over time this rubbing reduces the thickness and therefore strength of the Jewellery part. This occurs where moving parts of the piece touch each other such as the links in a chain or the bale on a pendant where the chain runs through it. Rings on the finger will wear each other flat when worn together over time. Jewellery stored together improperly can wear together causing unwanted and expensive damage.
The Fonya lockit is an innovative new product designed to securely hold the wearers rings on a neck chain keeping them safe when they cannot be worn. An important consideration in the design process involves calculating the softness of alloys commonly used in rings and how the Fonya lockit would impact the ring. Consideration of the contact area size and shape is paramount, if the pendant is sharp or has an awkward contact area it will certainly wear a groove in the ring. Further, the alloy of the pendant needed to act as a reliable spring to keep the locket secure without the addition of steel. Read more about the locket at http://fonya.com.au/