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Thanks for all these detailed explanations. My 8 year old great grandaughter asked today and I thought it was something to do with weight but wasn't sure so decided to ask. They seem to cover all topics at her school ,at Easter she wanted to know did we believe in ghosts and when told there were no ghosts she said "Well what's all this about Jesus and the Holy Ghost.?" never a dull moment, of course my daughter, her Nana usually says ask Grandma May she'll know more about it than me, must think because I'm older I know everything, not so!! still learning.
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[edit] Measure
As a measure of purity, one carat is purity by mass:
where
X is the carat rating of the material,
Mg is the mass of pure gold or platinum in the material, and
Mm is the total mass of the material.
Therefore 24-carat gold is fine (99.9% Au w/w), 18-carat gold is 75% gold, 12-carat gold is 50% gold, and so forth.
Historically, in England the carat was divisible into four grains, and the grain was divisible into four quarts. For example, a gold alloy of fineness (that is, 99.2% purity) could have been described as being 23-carat, 3-grain, 1-quart gold.
The carat system is increasingly being complemented or superseded by the millesimal fineness system in which the purity of precious metals is denoted by parts per thousand of pure metal in the alloy.
The most common carats used for gold in bullion, jewelry making and by goldsmiths are:
24 carat (millesimal fineness 999 or higher)
22 carat (millesimal fineness 916)
20 carat (millesimal fineness 833)
18 carat (millesimal fineness 750)
15 carat (millesimal fineness 625)
14 carat (millesimal fineness 585)
10 carat (millesimal fineness 417)
9 carat (millesimal fineness 375)
8 carat (millesimal fineness 333)
1 carat (millesimal fineness 042)
[edit] Derivation
The word carat is derived from the Greek kerátion (κεράτιoν), “fruit of the carob”, via Arabic qīrāṭ (قيراط) and Italian carato. Carob seeds were used as weights on precision scales because of their reputation for having a uniform weight. (However, a 2006 study[1] by Lindsay Turnbull and others found this to not be the case – carob seeds have as much variation in their weights as other seeds.[2]) This was not the only reason. It is said that in order to keep regional buyers and sellers of gold honest, a potential customer could retrieve their own carob seeds on their way to the market, to check the tolerances of the seeds used by the merchant. If this precaution was not taken, the potential customer would be at the mercy of "2 sets of carob seeds". One set of "heavier" carob seeds would be used when buying from a customer (making the seller's gold appear to be less). Another, lighter set of carob seeds would be used when the merchant wanted to sell to a customer.
In the distant past, different countries each had their own carat, roughly equivalent to a carob seed. In the mid-16th century, the Karat was adopted as a measure of gold purity, roughly equivalent to the Roman siliqua ( of a golden solidus of Constantine I). As a measure of diamond weight, from 1575, the Greek measure was the equivalent of the Roman siliqua, which was of a golden solidus of Constantine; but was likely never used to measure the weight for gold.[3]
[edit] Terminology
22/22K - a quality mark indicating the purity of gold most popularly used in India. This purity was adapted and practiced by the big jewellers and was later passed to jewel smiths. The first 22 signifies the "Skin purity", the purity of the top layer of the gold jewelry, and the second 22 signifies that after melting purity of the gold jewellery will be 22-carat, or 91.67% of pure gold. This system is used to show consistency in the quality of the gold.
This symbol or stamp is very popular on the gold jewellery business in Asian countries like India, Sri Lanka, Pakistan, Bangladesh, Nepal, Yemen, and Persian Gulf countries.
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its to show the purity of the gold,,,,ie parts of,,,,
dates back hundreds of years when a weight a (carat ) a bean was used to weigh pure gold,just like we use weighing scale weights,,,,,
pure gold doesnt have any carat weight,,,
so a measure of alloy how much weight of alloy is levied against the gold,,,,,ensures wearability.....
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Hi hope this helps
SOME FACTS ABOUT GOLD
The chemical symbol for gold is Au, from the Latin aurum, which means 'shining dawn'. Aurora was the Roman goddess of dawn which links to the warm, yellow colour of gold. Gold and Copper are the only two non white coloured metals.
Gold and copper were the first metals to be discovered by man, around 5000BC, and together with silver these three metals are found in the metallic state in the earth's crust. Gold is still mined in its metallic form in over 60 countries around the world.
Gold is referred to as a precious and a noble metal. Gold has an excellent chemical stability with a high resistance to corrosion and oxidation. However, this is just one of the many properties that gold possesses, which when considered in combination with each other have led to a number of exciting and often unique industrial applications.
The purity of gold is measured in Carats. A Carat was originally a unit of mass (weight) based on the Carob seed or bean which was used by ancient merchants in the Middle East. The Carat is still used for the weight of gem stones where 1 carat = 200mg. For gold is is used to measure the purity where pure gold is 24 carats. The following table shows the range from pure gold at 24 Carats to less pure at 9 Carats.
Native Scottish gold is amongst the purest at 22.8 carats!!!
Pure gold
Gold alloys
Carats
Fineness
% Gold
24
1000
100
22
916.7
91.67
18
750
75
14
583.3
58.3
10
416.7
41.67
9
375
37.5
In Europe 18 and 14 carat alloys are most commonly used in jewellery, however 9 carat is popular in Britain.
In many countries the law requires that every item of gold jewellery is clearly stamped with its caratage. Jewellery in many countries is stamped or hallmarked with its caratage. The hallmarking system was developed in London in the 14th century at Goldsmiths' Hall
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Why is gold measured in carrats?
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