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===Platinum=== |
===Platinum=== |
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* 999. |
* 999.95: what most dealers would buy as if 100% pure; the most common purity for platinum bullion coins and bars |
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* 999—''three [[nine (purity)|nines]] fine'' |
* 999—''three [[nine (purity)|nines]] fine'' |
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* 950: the most common purity for platinum jewelry |
* 950: the most common purity for platinum jewelry |
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* 500—''12 karat'' |
* 500—''12 karat'' |
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* 417—''10 karat'': Lowest legal solid gold karat made in the US prior to the August 2018 revision of the FTC Guides (Now 1 karat is legal). |
* 417—''10 karat'': Lowest legal solid gold karat made in the US prior to the August 2018 revision of the FTC Guides (Now 1 karat is legal). |
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* 375—''9 karat'': Minimum standard for gold in |
* 375—''9 karat'': Minimum standard for gold in some of the Commonwealth realms: Australia, Canada, New Zealand, UK, etc. It is also the minimum in Austria, Ireland, Portugal and France. |
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* 333—''8 karat'': Minimum standard for gold in Germany after 1884<ref>{{cite web|url=http://goldratefortoday.org/fineness-of-gold/ |title=Fineness of Gold |publisher=Gold Rate for Today |access-date=2013-08-15 |url-status=dead |archive-url=https://web.archive.org/web/20130807053413/http://goldratefortoday.org/fineness-of-gold/ |archive-date=August 7, 2013 }}</ref> |
* 333—''8 karat'': Minimum standard for gold in Germany after 1884.<ref>{{cite web|url=http://goldratefortoday.org/fineness-of-gold/ |title=Fineness of Gold |publisher=Gold Rate for Today |access-date=2013-08-15 |url-status=dead |archive-url=https://web.archive.org/web/20130807053413/http://goldratefortoday.org/fineness-of-gold/ |archive-date=August 7, 2013 }}</ref> It is also the minimum for Denmark, Greece and Mexico. |
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* ''1 karat'': Legal minimum for gold in the US since the revision of the FTC Guides of August 2018. |
* ''1 karat'': Legal minimum for gold in the US since the revision of the FTC Guides of August 2018. |
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===Silver=== |
===Silver=== |
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[[File:2019 American Silver Eagle and 1943 Walking Liberty Half dollar side by side.jpg|thumb|A 2019 [[American Silver Eagle]] [[bullion coin]] with a fineness of 999 (three nines fine), together with a [[Walking Liberty half dollar]] with a fineness of 900 (one nine fine).]] |
[[File:2019 American Silver Eagle and 1943 Walking Liberty Half dollar side by side.jpg|thumb|A 2019 [[American Silver Eagle]] [[bullion coin]] with a fineness of 999 (three nines fine), together with a [[Walking Liberty half dollar]] with a fineness of 900 (one nine fine); this latter alloy is also often referred to as ''90% silver'' or ''coin silver''.]] |
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* 999.99—''five nines fine'': The purest silver ever produced. This was achieved by the Royal Silver Company of Bolivia.<ref>{{cite web|url=http://www.royalsilver.com/about_us/about_us.html|title=..:: Royal Silver Company ::..|url-status=live|archive-url=https://web.archive.org/web/20130316133926/http://www.royalsilver.com/about_us/about_us.html|archive-date=2013-03-16}}</ref> |
* 999.99—''five nines fine'': The purest silver ever produced. This was achieved by the Royal Silver Company of Bolivia.<ref>{{cite web|url=http://www.royalsilver.com/about_us/about_us.html|title=..:: Royal Silver Company ::..|url-status=live|archive-url=https://web.archive.org/web/20130316133926/http://www.royalsilver.com/about_us/about_us.html|archive-date=2013-03-16}}</ref> |
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* 999.9—''four [[nine (purity)|nines]] fine'': ultra-fine silver used by the Royal Canadian Mint for their [[Canadian Silver Maple Leaf|Silver Maple Leaf]] and other silver coins |
* 999.9—''four [[nine (purity)|nines]] fine'': ultra-fine silver used by the Royal Canadian Mint for their [[Canadian Silver Maple Leaf|Silver Maple Leaf]] and other silver coins |
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* 917: a standard used for the minting of Indian silver ([[rupees]]), during the British raj and for some coins during the first Brazilian Republic. |
* 917: a standard used for the minting of Indian silver ([[rupees]]), during the British raj and for some coins during the first Brazilian Republic. |
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* 916: 88 zolotnik Russian silver |
* 916: 88 zolotnik Russian silver |
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* 900: ''one [[nine (purity)|nine]] fine'', ''coin-silver'' |
* 900: ''one [[nine (purity)|nine]] fine'', ''coin-silver'', or ''90% silver'': e.g. [[Flowing Hair]] and 1837–1964 U.S. silver coins. Also used in U.S. silver [[commemorative coin]]s and silver [[proof coin]]s 1982–2018. |
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* 892.4: US coinage {{frac|1485|1664}} fine "standard silver" as defined by the [[Coinage Act of 1792]]: e.g. [[Draped Bust]] and [[Capped Bust]] U.S. silver coins (1795–1836) |
* 892.4: US coinage {{frac|1485|1664}} fine "standard silver" as defined by the [[Coinage Act of 1792]]: e.g. [[Draped Bust]] and [[Capped Bust]] U.S. silver coins (1795–1836) |
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* 875: 84 zolotnik is the most common fineness for Russian silver. Swiss standard, commonly used for export watchcases (also 800 and later 935). |
* 875: 84 zolotnik is the most common fineness for Russian silver. Swiss standard, commonly used for export watchcases (also 800 and later 935). |
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* 868: 83 {{frac|1|3}} zolotnik. Imperial Russian coinage between 1797<ref>{{Cite web|title=1 Rouble, Paul I, Russian Empire|url=https://en.numista.com/catalogue/pieces26955.html|access-date=2024-03-22|website=en.numista.com|language=en}}</ref> and 1885.<ref>{{Cite web|title=1 Rouble, Alexander II-III, Russian Empire|url=https://en.numista.com/catalogue/pieces16511.html|access-date=2024-03-22|website=en.numista.com|language=en}}</ref> |
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* 835: A standard predominantly used in Germany after 1884, and for some Dutch silver; and for the minting of coins in countries of the [[Latin Monetary Union]] |
* 835: A standard predominantly used in Germany after 1884, and for some Dutch silver; and for the minting of coins in countries of the [[Latin Monetary Union]] |
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* 833: ({{frac|5|6}}) a common standard for continental silver especially among the Dutch, Swedish, and Germans |
* 833: ({{frac|5|6}}) a common standard for continental silver especially among the Dutch, Swedish, and Germans |
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* 800: The minimum standard for silver in Germany after 1884; the French 2nd standard for silver; "plata de segunda ley" in Spain (second law silver); Egyptian silver; Canadian silver circulating coinage from 1920-1966/7<ref>{{Cite web|url=http://www.coinflation.com/canada/|title=Canadian Coin Melt Values - Coinflation|website=www.coinflation.com|access-date=2017-11-12|url-status=live|archive-url=https://web.archive.org/web/20170617215506/http://www.coinflation.com/canada/|archive-date=2017-06-17}}</ref> |
* 800: The minimum standard for silver in Germany after 1884; the French 2nd standard for silver; "plata de segunda ley" in Spain (second law silver); Egyptian silver; Canadian silver circulating coinage from 1920-1966/7<ref>{{Cite web|url=http://www.coinflation.com/canada/|title=Canadian Coin Melt Values - Coinflation|website=www.coinflation.com|access-date=2017-11-12|url-status=live|archive-url=https://web.archive.org/web/20170617215506/http://www.coinflation.com/canada/|archive-date=2017-06-17}}</ref> |
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* 750: An uncommon silver standard found in older German, Swiss and [[Austro-Hungarian]] silver |
* 750: An uncommon silver standard found in older German, Swiss and [[Austro-Hungarian]] silver |
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* 720: Decoplata |
* 720: Decoplata:<ref>{{Cite web | url=https://coinweek.com/world-coins/decoplata-the-history-of-720-silver-in-world-coinage/ | title=Decoplata: The History of .720 Silver in World Coinage | date=18 January 2022 }}</ref> many Mexican and Dutch silver coins use this standard, as well as some coins from Portugal's former colonies,<ref>{{Cite web|title=10 Escudos, Angola|url=https://en.numista.com/catalogue/pieces6538.html|access-date=2021-11-04|website=en.numista.com|language=en}}</ref> Japan,<ref>{{Cite web|title=10 Sen - Taishō, Japan|url=https://en.numista.com/catalogue/pieces14003.html|access-date=2021-11-13|website=en.numista.com|language=en}}</ref> Uruguay,<ref>{{Cite web|title=1 Peso, Uruguay|url=https://en.numista.com/catalogue/pieces10344.html|access-date=2021-11-04|website=en.numista.com|language=en}}</ref> Ecuador, Egypt, and Morocco. |
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* 600: Used in some examples of postwar [[Japan]]ese [[Japanese yen#Coins|coins]], such as the 1957-1966 [[100 yen coin]] |
* 600: Used in some examples of postwar [[Japan]]ese [[Japanese yen#Coins|coins]], such as the 1957-1966 [[100 yen coin]] |
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* 500: Standard used for making British coinage 1920–1946 as well as Canadian coins from 1967-1968, and some coins from Colombia and Brazil. |
* 500: Standard used for making British coinage 1920–1946 as well as Canadian coins from 1967-1968, and some coins from Colombia and Brazil. |
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=== Mass === |
=== Mass === |
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:''K'' = 24 × ''M''<sub>g</sub> / ''M''<sub>m</sub> |
:''K'' = 24 × (''M''<sub>g</sub> / ''M''<sub>m</sub>) |
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where |
where |
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===Volume=== |
===Volume=== |
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However, this system of calculation gives only the mass of pure gold contained in an alloy. The term ''18-karat gold'' means that the alloy's mass consists of 75% of gold and 25% of other metals. The quantity of gold ''by volume'' in a less-than-24-karat gold alloy differs according to the alloys used. For example, knowing that standard 18-karat yellow gold consists of 75% gold, 12.5% silver and the remaining 12.5% of copper (all by mass), the volume of pure gold in this alloy will be 60% since gold is much denser than the other metals used: 19.32 g/cm<sup>3</sup> for gold, 10.49 g/cm<sup>3</sup> for silver and 8.96 g/cm<sup>3</sup> for copper. |
However, this system of calculation gives only the mass of pure gold contained in an alloy. The term ''18-karat gold'' means that the alloy's mass consists of 75% of gold and 25% of other metals. The quantity of gold ''by volume'' in a less-than-24-karat gold alloy differs according to the alloys used. For example, knowing that standard 18-karat yellow gold consists of 75% gold, 12.5% silver and the remaining 12.5% of copper (all by mass), the volume of pure gold in this alloy will be 60% since gold is much denser than the other metals used: 19.32 g/cm<sup>3</sup> for gold, 10.49 g/cm<sup>3</sup> for silver and 8.96 g/cm<sup>3</sup> for copper. |
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This formula gives the amount of gold in cubic centimeters or in milliliters in an alloy: |
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: <math>V_\text{Au} = \frac{M_\text{a} \times \frac{kt}{24}}{19.32}</math> |
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where |
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: ''V''<sub>Au</sub> is the volume of gold in cubic centimeters or in milliliters |
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: ''M''<sub>a</sub> is the total mass of the alloy in grams |
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: ''kt'' is the karat purity of the alloy |
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To have the percentage of the volume of gold in an alloy, divide the volume of gold in cubic centimeters or in milliliters by the total volume of the alloy in cubic centimeters or in milliliters. |
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For 10-carat gold, the gold volume in the alloy represents about 26% of the total volume for standard yellow gold. |
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===Etymology=== |
===Etymology=== |
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''Karat'' is a variant of ''carat''. First attested in English in the mid-15th century, the word ''carat'' came from [[Middle French]] {{lang|frm|carat}}, in turn derived either from Italian {{lang|it|carato}} or Medieval Latin {{lang|la|carratus}}. These were borrowed into Medieval Europe from the [[Arabic language|Arabic]] {{lang|ar-Latn|qīrāṭ}} meaning "fruit of the carob tree", also "weight of 5 grains", ({{lang|ar|قيراط|rtl=yes}}) and was a unit of mass<ref>[http://oxforddictionaries.com/view/entry/m_en_gb0122990#m_en_gb0122990 carat] {{webarchive|url=https://web.archive.org/web/20101024043951/http://oxforddictionaries.com/view/entry/m_en_gb0122990 |date=2010-10-24 }}, Oxford Dictionaries</ref> though it was probably not used to measure gold in classical times.<ref name=harper/> The Arabic term ultimately originates from the [[Greek language|Greek]] {{lang|el-Latn|kerátion}} ({{lang|el|κεράτιον}}) meaning [[carob]] seed (literally "small horn")<ref name=harper>{{OEtymD|carat|accessdate=}}</ref><ref>[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dkera%2Ftion κεράτιον] {{webarchive|url=https://web.archive.org/web/20121008220045/http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry=kera%2Ftion |date=2012-10-08 }}, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref><ref>Walter W. Skeat (1888), ''[https://archive.org/details/etymologicaldict00skeauoft An Etymological Dictionary of the English Language]''</ref> (diminutive of {{lang|el|κέρας}} – {{lang|el-Latn|kéras}}, "horn"<ref>[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dke%2Fras κέρας] {{webarchive|url=https://web.archive.org/web/20121008220111/http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry=ke%2Fras |date=2012-10-08 }}, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref>). |
''Karat'' is a variant of ''carat''. First attested in English in the mid-15th century, the word ''carat'' came from [[Middle French]] {{lang|frm|carat}}, in turn derived either from Italian {{lang|it|carato}} or Medieval Latin {{lang|la|carratus}}. These were borrowed into Medieval Europe from the [[Arabic language|Arabic]] {{lang|ar-Latn|qīrāṭ}} meaning "fruit of the carob tree", also "weight of 5 grains", ({{lang|ar|قيراط|rtl=yes}}) and was a unit of mass<ref>[http://oxforddictionaries.com/view/entry/m_en_gb0122990#m_en_gb0122990 carat] {{webarchive|url=https://web.archive.org/web/20101024043951/http://oxforddictionaries.com/view/entry/m_en_gb0122990 |date=2010-10-24 }}, Oxford Dictionaries</ref> though it was probably not used to measure gold in classical times.<ref name=harper/> The Arabic term ultimately originates from the [[Greek language|Greek]] {{lang|el-Latn|kerátion}} ({{lang|el|κεράτιον}}) meaning [[carob]] seed (literally "small horn")<ref name=harper>{{OEtymD|carat|accessdate=}}</ref><ref>[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dkera%2Ftion κεράτιον] {{webarchive|url=https://web.archive.org/web/20121008220045/http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry=kera%2Ftion |date=2012-10-08 }}, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref><ref>Walter W. Skeat (1888), ''[https://archive.org/details/etymologicaldict00skeauoft An Etymological Dictionary of the English Language]''</ref> (diminutive of {{lang|el|κέρας}} – {{lang|el-Latn|kéras}}, "horn"<ref>[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dke%2Fras κέρας] {{webarchive|url=https://web.archive.org/web/20121008220111/http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry=ke%2Fras |date=2012-10-08 }}, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref>). |
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In 309 |
In 309 AD, [[Roman Emperor]] [[Constantine I]] began to [[mint (coin)|mint]] a new gold coin ''[[solidus (coin)|solidus]]'' that was {{frac|72}} of a ''[[Ancient Roman units of measurement#Mass|libra]]'' (Roman pound) of gold<ref>{{cite book|last=Vagi|first=David L.|title=Coinage and History of the Roman Empire|url=https://books.google.com/books?id=pH9Ok9czKsMC&pg=PA100|access-date=18 November 2011|volume=II: Coinage|year=1999|publisher=Fitzroy Dearborn|location=Chicago|isbn=978-1-57958-316-3|page=100|url-status=live|archive-url=https://web.archive.org/web/20130607010928/http://books.google.com/books?id=pH9Ok9czKsMC&pg=PA100|archive-date=7 June 2013}}</ref> equal to a mass of 24 ''[[siliqua]]e'', where each siliqua (or [[carat (mass)|carat]]) was {{frac|1728}} of a libra.<ref>{{cite book|last=Grierson|first=Philip|title=Catalogue of the Byzantine Coins in the Dumbarton Oaks Collection and in the Whittemore Collection|url=https://books.google.com/books?id=l97WJwbuAWsC&pg=PA8|access-date=18 November 2011|volume=2: pt. 1|year=1968|publisher=Dumbarton Oaks|location=Washington, DC|isbn=978-0-88402-024-0|page=8|url-status=live|archive-url=https://web.archive.org/web/20130606220053/http://books.google.com/books?id=l97WJwbuAWsC&pg=PA8|archive-date=6 June 2013}}</ref> This is believed to be the origin of the value of the karat.<ref>{{Cite journal | last1 = Turnbull | first1 = L. A. | last2 = Santamaria | first2 = L. | last3 = Martorell | first3 = T. | last4 = Rallo | first4 = J. | last5 = Hector | first5 = A. | title = Seed size variability: From carob to carats | journal = Biology Letters | volume = 2 | issue = 3 | pages = 397–400 | year = 2006 | pmid = 17148413 | pmc = 1686184 | doi = 10.1098/rsbl.2006.0476}}</ref> |
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==Verifying fineness== |
==Verifying fineness== |
The fineness of a precious metal object (coin, bar, jewelry, etc.) represents the weight of fine metal therein, in proportion to the total weight which includes alloying base metals and any impurities. Alloy metals are added to increase hardness and durability of coins and jewelry, alter colors, decrease the cost per weight, or avoid the cost of high-purity refinement. For example, copper is added to the precious metal silver to make a more durable alloy for use in coins, housewares and jewelry. Coin silver, which was used for making silver coins in the past, contains 90% silver and 10% copper, by mass. Sterling silver contains 92.5% silver and 7.5% of other metals, usually copper, by mass.
Various ways of expressing fineness have been used and two remain in common use: millesimal fineness expressed in units of parts per 1,000[1] and karatsorcarats used only for gold. Karats measure the parts per 24, so that 18 karat = 18⁄24 = 75% and 24 karat gold is considered 100% gold.[2]
Millesimal fineness is a system of denoting the purity of platinum, gold and silver alloysbyparts per thousand of pure metal by mass in the alloy. For example, an alloy containing 75% gold is denoted as "750". Many European countries use decimal hallmark stamps (i.e., "585", "750", etc.) rather than "14 k", "18 k", etc., which is used in the United Kingdom and United States.
It is an extension of the older karat system of denoting the purity of gold by fractions of 24, such as "18 karat" for an alloy with 75% (18 parts per 24) pure gold by mass.
The millesimal fineness is usually rounded to a three figure number, particularly where used as a hallmark, and the fineness may vary slightly from the traditional versions of purity.
Here are the most common millesimal finenesses used for precious metals and the most common terms associated with them.
The karat (US spelling, symbol korKt) or carat (UK spelling, symbol corCt)[17][18] is a fractional measure of purity for gold alloys, in parts fine per 24 parts whole. The karat system is a standard adopted by US federal law.[19]
where
24-karat gold is pure (while 100% purity is very difficult to attain, 24-karat as a designation is permitted in commerce for a minimum of 99.95% purity), 18-karat gold is 18 parts gold, 6 parts another metal (forming an alloy with 75% gold), 12-karat gold is 12 parts gold (12 parts another metal), and so forth.[20]
In England, the carat was divisible into four grains, and the grain was divisible into four quarts. For example, a gold alloy of 127⁄128 fineness (that is, 99.2% purity) could have been described as being 23-karat, 3-grain, 1-quart gold.
The karat fractional system is increasingly being complemented or superseded by the millesimal system, described above for bullion, though jewelry generally tends to still use the karat system.
Conversion between percentage of pure gold and karats:
However, this system of calculation gives only the mass of pure gold contained in an alloy. The term 18-karat gold means that the alloy's mass consists of 75% of gold and 25% of other metals. The quantity of gold by volume in a less-than-24-karat gold alloy differs according to the alloys used. For example, knowing that standard 18-karat yellow gold consists of 75% gold, 12.5% silver and the remaining 12.5% of copper (all by mass), the volume of pure gold in this alloy will be 60% since gold is much denser than the other metals used: 19.32 g/cm3 for gold, 10.49 g/cm3 for silver and 8.96 g/cm3 for copper.
Karat is a variant of carat. First attested in English in the mid-15th century, the word carat came from Middle French carat, in turn derived either from Italian carato or Medieval Latin carratus. These were borrowed into Medieval Europe from the Arabic qīrāṭ meaning "fruit of the carob tree", also "weight of 5 grains", (قيراط) and was a unit of mass[21] though it was probably not used to measure gold in classical times.[22] The Arabic term ultimately originates from the Greek kerátion (κεράτιον) meaning carob seed (literally "small horn")[22][23][24] (diminutive of κέρας – kéras, "horn"[25]).
In 309 AD, Roman Emperor Constantine I began to mint a new gold coin solidus that was 1⁄72 of a libra (Roman pound) of gold[26] equal to a mass of 24 siliquae, where each siliqua (orcarat) was 1⁄1728 of a libra.[27] This is believed to be the origin of the value of the karat.[28]
While there are many methods of detecting fake precious metals, there are realistically only two options available for verifying the marked fineness of metal as being reasonably accurate: assaying the metal (which requires destroying it), or using X-ray fluorescence (XRF). XRF will measure only the outermost portion of the piece of metal and so may get misled by thick plating.
That becomes a concern because it would be possible for an unscrupulous refiner to produce precious metals bars that are slightly less pure than marked on the bar. A refiner doing $1 billion of business each year that marked .980 pure bars as .999 fine would make about an extra $20 million in profit. In the United States, the actual purity of gold articles must be no more than .003 less than the marked purity (e.g. .996 fine for gold marked .999 fine), and the actual purity of silver articles must be no more than .004 less than the marked purity.[29]
A piece of alloy metal containing a precious metal may also have the weight of its precious component referred to as its "fine weight". For example, 1 troy ounce of 18 karat gold (which is 75% gold) may be said to have a fine weight of 0.75 troy ounces.
Most modern government-issued bullion coins specify their fine weight. For example, the American Gold Eagle is embossed One Oz. Fine Gold and weighs 1.091 troy oz.
Fineness of silver in Britain was traditionally expressed as the mass of silver expressed in troy ounces and pennyweights (1⁄20 troy ounce) in one troy pound (12 troy ounces) of the resulting alloy. Britannia silver has a fineness of 11 ounces, 10 pennyweights, or about silver, whereas sterling silver has a fineness of 11 ounces, 2 pennyweights, or exactly
silver.
In October 2007, the Million Dollar Coin was certified by Guinness World Records to be the world's largest gold coin.
in a perception experiment observers could discriminate differences in carob seed weight of around 5% by eye... suggesting that human rather than natural selection gave rise to the carob myth