Purity: The purest form of Gold considered 24 karats is equal to roughly 99.9 percent purity. Sometimes when looking at the stamp inside of gold rings, bracelets or other gold jewellery the numerical expression is stamped in either a Karat volume or a metric unit. This guide can clear the confusion up. This guide doesn't deal with Chinese, Arabic or Hebrew symbols for Gold. It focuses solely on European and North American stamps and their corelating values.
Karat: When we say 24kt or 24k Gold jewelry, we mean that all the 24 parts in the gold are just pure gold without traces of any other metal(s) or 99.9 percent pure. When we say 22kt or 22k Gold Jewelry we mean that 22 parts of the jewelry, is gold and the balance 2 parts are some other metal(s) or equal to 91.3 percent gold plus 8.6 percent of some other metal alloy When we say 18Kt or 18k Gold Jewelry, we mean that 18 parts of the jewelry is gold and the balance 6 parts is some other metal or equal to about 75 percent gold plus 25 percent of some other metal alloy We can roughly state that each Karat is equal to approximately 4.1625 percent. The difference of the other metal or alloys of the metal, gives the jewelry its hardness and color. We can state that 24 Karat is the softest and 10 karat the hardest, because 10kt would have 41.6 percent gold and the balance would be other metals which are mostly harder than gold.. The color from the other metals enhances the beauty of the jewelry as the case may be, white gold, yellow gold, red gold etc.
Pure gold is too soft to be of much use in jewellery making. Therefore, gold is mixed with other metals and then used to make jewellery. The resulting alloy is known as "karat gold". Karat is a measure of the proportion of gold used in the alloy, and is expressed in parts out of 24. It is not the same as "carat" which is used to measure the weight of diamonds and gemstones.
Pure gold is 24 karats.
18 karat gold is 18/24th or 75% pure gold.
14 karat gold is 14/24th or 58.3% pure gold
10 karat gold is 10/24th or 41.7% pure gold
Karat is usually abbreviated to K, so 10 karat gold is expressed as 10K gold.
Most countries have laws regarding what can be called real gold. For example in US, gold has to be at least 10 karat to be called "real gold". In Australia, Canada and the UK the minimum is 9 karats. In Germany it is 8 karats.
Higher karat gold is generally more expensive. 18 karat gold is usually used in high end fine jewellery. Gold above 18 karats is rare, although in some countries (for example India) 22 karat gold is used.
Solid gold is often stamped or branded, either with its karat symbol or with the percentage representating the carat.
The stamps for percentage and karat symbol for gold expressed as follows:
333 - 8K gold
375 - 9k gold (vey popular in the old world, especially pre WWII UK)
417 - 10K gold
500 - 12K gold
585 - 14K gold
666 - 16K gold (gold teeth and fillings)
750 - 18K gold
792 - 19K gold (used in portugal)
833 - 20K
916 - 22k gold
999 - 24K gold
You may have noticed that the stamp for the 14K gold is slightly higher than the actual percentage of pure gold in that karatage. This is because in Europe there is a practice of putting a slightly higher percentage of gold into what we call 14K gold (ie they put 58.5% instead of 58.3%).
This guide is as good as gold.