View source for Fineness

{{short description|Weight of fine metal in a precious metal object}}
{{distinguish| Fineness ratio}}
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 [[alloy]]ing [[base metal]]s and any [[impurity|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 coin]]s in the past, contains 900 ‰ silver and 100 ‰ copper, by [[mass]]. [[Sterling silver]] contains 925 ‰ silver and 75 ‰ 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 [[per mil|parts per 1,000]]<ref>{{cite web |last=London Bullion Market Association |title=Definitions |url=http://www.lbma.org.uk/market-tools |url-status=live |archive-url=https://web.archive.org/web/20150712152226/http://www.lbma.org.uk/Market-Tools |archive-date=2015-07-12 }}</ref> and ''[[#Karat|karats]]'' or ''carats'' used only for [[gold]]. Karats measure the parts per 24, so that 18 karat = {{frac|18|24}} = 750 ‰ and 24 karat gold is considered 100% gold.<ref>{{cite book |last=Seyd |first=Ernest |title=Bullion and foreign exchanges theoretically and practically considered |url=https://archive.org/details/bullionandforei01seydgoog |access-date=21 March 2012 |year=1868 |publisher=E. Wilson |page=[https://archive.org/details/bullionandforei01seydgoog/page/n158 146] }}</ref>

==Millesimal fineness==
Millesimal fineness is a system of denoting the purity of [[platinum]], [[gold]] and [[silver]] [[alloy]]s by [[Per mille|parts 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 metal]]s and the most common terms associated with them.

===Platinum===
* 999.95: what most dealers would buy as if 100% pure; the most common purity for platinum bullion coins and bars
* 999—''three [[nine (purity)|nines]] fine''
* 950: the most common purity for platinum jewelry
* 900—''one nine fine''
* 850
* 750

===Gold===
[[Image:Four nines fine gold.jpeg|thumb|upright|1 [[troy ounce]] of four nines fine gold (999.9)]]
* 999.999—''six [[nine (purity)|nines]] fine'': The purest gold ever produced. Refined by the [[Perth Mint]] in 1957.<ref>{{cite web |url=http://www.perthmint.com.au/visit_the_mint_the_perth_mint_history.aspx |title=The Perth Mint :: History |publisher=Gold Corporation |access-date=2011-05-08 |url-status=live |archive-url=https://web.archive.org/web/20110514024331/http://www.perthmint.com.au/visit_the_mint_the_perth_mint_history.aspx |archive-date=2011-05-14 }}</ref><ref>{{cite book |last=Thomas |first=Athol |title=90 Golden Years, The story of the Perth Mint |publisher=Gold Corporation |page=58}}</ref>
* 999.99—''five nines fine'': The purest type of gold currently produced; the [[Royal Canadian Mint]] regularly produces commemorative coins in this fineness, including the world's largest, at 100&nbsp;kg.<ref>{{cite web|url=http://www.mint.ca/store/mint/about-the-mint/million-dollar-coin-1600006|title=The Million Dollar Coin – a true milestone in minting|author=Royal Canadian Mint|access-date=13 July 2017|quote=In October 2007, the Million Dollar Coin was certified by Guinness World Records to be the world's largest gold coin.|url-status=live|archive-url=https://web.archive.org/web/20150309153548/http://www.mint.ca/store/mint/about-the-mint/million-dollar-coin-1600006|archive-date=9 March 2015}}</ref>
* 999.9—''four nines fine'': Most popular. E.g. ordinary [[Canadian Gold Maple Leaf]] and [[American Buffalo (coin)|American Buffalo]] coins.
* 999—''24 karat'', also occasionally known as ''three nines fine'': e.g., [[Chinese Gold Panda]] coins.
* 995: The minimum allowed in [[Good Delivery]] gold bars.
* 990—''two nines fine''
* 986—''[[Ducat]] fineness'': Formerly used by Venetian and Holy Roman Empire mints; still in use in Austria and Hungary.
* 958.3—''23 karat''
* 916—''22 karat'': [[Crown gold]]. Historically the most widely used fineness for gold bullion coins, such as the oldest American [[Eagle (United States coin)|Eagle]] denominations from 1795–1833.  Currently used for [[Sovereign (British coin)|British Sovereigns]], [[Krugerrand|South African Krugerrands]], and the modern (1986—present) [[American Gold Eagle]]s.
* 900—''one nine fine'': American Eagle denominations for 1837–1933; currently used in [[Latin Monetary Union]] mintage (e.g. French and Swiss "[[Napoleon (coin)|Napoleon coin]]" 20 francs).
* 899—American Eagles briefly for 1834—1836.
* 834—''20 karat''
* 750—''18 karat'': In Spain ''oro de primera ley''  (first law gold).
* 625—''15 karat''
* 585—''14 karat''
* 583.3—''14 karat'': In Spain ''oro de segunda ley'' (second law gold).
* 500—''12 karat''
* 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). 
* 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.
* 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.
* ''1 karat'': Legal minimum for gold in the US since the revision of the FTC Guides of August 2018.

===Silver===
{{see also|Silver standards}}
[[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''.]]
* 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>
* 999.9—''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—''fine silver'' or ''three nines fine'': used in [[Good Delivery]] bullion bars and most current [[Bullion coin#Silver|silver bullion coins]].  Used in U.S. silver [[commemorative coin]]s and silver [[proof coin]]s starting in 2019.<ref>[https://www.coinworld.com/news/precious-metals/us-mint-drops-90-percent-silver-composition.html U.S. Mint abandons 90 percent silver composition]</ref>
* 980: common standard used in Mexico ca. 1930–1945
* 958: ({{frac|23|24}}) ''[[Britannia silver]]''<ref name="Silver standards">{{cite web | url=https://www.antiquesinoxford.co.uk/silver-standards | title=Silver standards | publisher=Antiques in Oxford | access-date=2020-10-05}}</ref>
* 950: ''French 1st Standard''
* 947.9: 91 [[zolotnik]] Russian silver
* 935: Swiss standard for watchcases after 1887, to meet the British [[Merchandise Marks Act 1887|Merchandise Marks Act]] and to be of equal grade to 925 sterling. Sometimes claimed to have arisen as a Swiss misunderstanding of the standard required for British sterling. Usually marked with three Swiss bears.
* 935: used in the Art Deco period in Austria and Germany. Scandinavian silver jewellers used 935 silver after the 2nd World War
* 925: ({{frac|37|40}}) ''[[Sterling silver]]''. The UK has used this alloy from the early 12th century. Equivalent to ''plata de primera ley'' in Spain (first law silver)
* 917: a standard used for the minting of Indian silver ([[rupees]]), during the British raj and for some coins during the first Brazilian Republic.
* 916: 88 zolotnik Russian 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.
* 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)
* 875: 84 zolotnik is the most common fineness for Russian silver. Swiss standard, commonly used for export watchcases (also 800 and later 935).
* 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>
* 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]]
* 833: ({{frac|5|6}}) a common standard for continental silver especially among the Dutch, Swedish, and Germans
* 830: A common standard used in older Scandinavian silver
* 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> Used for the outer cladding of US [[Half dollar (United States coin)|half dollar]]s between 1965 and 1970, and commemorative issue [[Eisenhower dollar]]s between 1971 and 1978 (cores are 20.9% silver)
* 750: An uncommon silver standard found in older German, Swiss and [[Austro-Hungarian]] silver
* 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.
* 600: Used in some examples of postwar [[Japan]]ese [[Japanese yen#Coins|coins]], such as the 1957-1966 [[100 yen coin]]
* 500: Standard used for making British coinage 1920–1946 as well as Canadian coins from 1967-1968, and some coins from Colombia and Brazil.
* 350: Standard used for US [[Jefferson nickel|Jefferson "war nickels"]] minted between 1942 and 1945.

=={{anchor|Karat|Carat|carat|karat}} Carat==
{{Redirect|Karat}}
The '''carat''' (UK spelling, symbol '''c''' or '''Ct''') or '''karat''' (US spelling, symbol '''k''' or '''Kt''') <ref>{{cite book |last=Melaragno |first=Michele |title=The VNR Dictionary of Engineering Units and Measures |publisher=Van Nostrand Reinhold |page=114}}</ref><ref>{{cite book |title=The VNR OXFORD Dictionary for Scientific Writers and Editors |publisher=Oxford University Press |page=56}}</ref> is a fractional measure of purity for [[gold]] [[alloys]], in parts fine per 24 parts whole. The carat system is a standard adopted by US federal law.<ref>{{cite web|url=https://www.law.cornell.edu/cfr/text/16/23.3|title=United States Code, 16 CFR 23.3 - Misrepresentation as to gold content.|url-status=live|archive-url=https://web.archive.org/web/20170214181016/https://www.law.cornell.edu/cfr/text/16/23.4|archive-date=2017-02-14}}</ref>

=== Mass ===

:''C'' = 24 &times; (''M''<sub>g</sub> / ''M''<sub>m</sub>)

where

: ''C'' is the carat rating of the material,
: ''M''<sub>g</sub> is the mass of pure gold in the alloy, and
: ''M''<sub>m</sub> is the total mass of the material.

24-carat gold is pure (while 100% purity is very difficult to attain, 24-carat as a designation is permitted in commerce for a minimum of 99.95% purity), 18-carat gold is 18 parts gold, 6 parts another metal (forming an alloy with 75% gold), 12-carat gold is 12 parts gold (12 parts another metal), and so forth.<ref>[http://www.gemsociety.org/article/fundametals-jewelery-metals-overview/ Comprehensive Jewelry Precious Metals Overview] {{webarchive|url=https://web.archive.org/web/20150217013036/http://www.gemsociety.org/article/fundametals-jewelery-metals-overview/ |date=2015-02-17 }} International Gem Society (IGS), Retrieved 01-16-2015</ref>

In England, the carat was divisible into four grains, and the grain was divisible into four quarts. For example, a gold alloy of {{frac|127|128}} fineness (that is, 99.2% purity) could have been described as being ''23-karat, 3-grain, 1-quart gold''.

The carat fractional system is increasingly being complemented or superseded by the [[#Millesimal fineness|millesimal]] system, described above for bullion, though jewelry generally tends to still use the carat system.

Conversion between percentage of pure gold and karats:
* 58.33–62.50% = 14 c (acclaimed 58.33%)
* 75.00–79.16% = 18 c (acclaimed 75.00%)
* 91.66–95.83% = 22 c (acclaimed 91.66%)
* 95.83–99.95% = 23 c (acclaimed 95.83%)
* 99.95–100% = 24 c (acclaimed 99.95%)

===Volume===
However, this system of calculation gives only the mass of pure gold contained in an alloy. The term ''18-carat 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-carat gold alloy differs according to the alloys used. For example, knowing that standard 18-carat 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&nbsp;g/cm<sup>3</sup> for gold, 10.49&nbsp;g/cm<sup>3</sup> for silver and 8.96&nbsp;g/cm<sup>3</sup> for copper.

===Etymology===
[[File:Ceratonia siliqua Pod and Seeds.jpg|thumb|Carob (''Ceratonia siliqua'') pod and seeds, origin of ''carat'' via Arabic {{lang|ar-Latn|qīrāṭ}} which itself comes from the Greek word for the seed {{lang|el-Latn|kerátion}}]]

''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>).

In 309{{nbs}}AD, [[Roman Emperor]] [[Constantine I]] began to [[mint (coin)|mint]] a new gold coin, the ''[[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>

==Verifying fineness==
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: [[Metallurgical assay|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&nbsp;billion of business each year that marked .980 pure bars as .999 fine would make about an extra $20&nbsp;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.<ref>{{cite web |title=15 U.S. Code Chapter 8 - FALSELY STAMPED GOLD OR SILVER OR GOODS MANUFACTURED THEREFROM |url=https://www.law.cornell.edu/uscode/text/15/chapter-8 |url-status=live |archive-url=https://web.archive.org/web/20161107050112/https://www.law.cornell.edu/uscode/text/15/chapter-8 |archive-date=2016-11-07 }}</ref>

==Fine weight==
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 750 ‰ 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.

==Troy mass of silver content==
Fineness of silver in [[UK|Britain]] was traditionally expressed as the [[mass]] of silver expressed in [[Troy weight|troy ounces]] and [[pennyweights]] ({{frac|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 <math> \frac{(11+\frac{10}{20})}{12}  = 95.833\% </math> silver, whereas [[sterling silver]] has a fineness of 11 ounces, 2 pennyweights, or exactly <math>\frac{(11+\frac{2}{20})}{12} = 92.5\%</math> silver.

==See also==
* [[Colored gold]]
* [[Electrum]]
* [[Gold as an investment]]
* [[Gold coin]]
* [[Platinum coin]]
* [[Silver as an investment]]
* [[Silver coin]]
* [[Tumbaga]]

== References ==
{{reflist|30em}}

==External links==
*{{wiktionary-inline|fineness}}
* {{cite journal |title= Seed size variability: From carob to carats |journal= Biology Letters |volume= 2 |issue= 3 |pages= 397–400 |date= Oct 2006 |doi= 10.1098/rsbl.2006.0476  |pmid= 17148413 |pmc= 1686184 |display-authors= 1 |first1= Lindsay A |last1= Turnbull |first2= Luis |last2= Santamaría |first3= Toni |last3= Martorell |first4= Joan |last4= Rallo|first5= Andy |last5= Hector |quote= 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 }}

[[Category:Metallurgy]]
[[Category:Gold investments]]
[[Category:Precious metals]]
[[Category:Units of purity]]
[[Category:Jewellery making]]

[[es:Ley (pureza)]]