{{short description|Weight of fine metal in a precious metal object}} {{distinguish| Fineness ratio}} {{more citations needed|date=May 2026}} 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 the 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<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 ''karats'' or ''carats'' used only for gold. Karats measure the parts per 24, so that 18 karat = {{frac|18|24}} = 75% gold 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 alloys by 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 States, and the United Kingdom prior to the 1970s.

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.

The most common millesimal finenesses used for precious metals and the most common terms for them are:

===Platinum=== * 999.95: what most dealers would buy as if 100% pure; the most common purity for platinum bullion coins and bars * 999—''three 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 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 in production; 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.|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 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. * 965: Thai standard for gold purity. Often considered equivalent to 23 karat in this context.<ref>{{cite web |url=https://sbma.org.sg/news/thailands-gold-market/ | title=Thailand's Gold Market| date=27 July 2017}}</ref> * 958—''23 karat'' * 916—''22 karat'': Crown gold. Historically common for bullion coins, and currently used for British Sovereigns, South African Krugerrands, and the modern (since 1986) American Gold Eagles. Standard for jewelry in some countries such as India.<ref name="Purity of gold">{{cite web |url=https://timesofindia.indiatimes.com/business/faqs/gold-faqs/purity-of-gold-difference-between-24k-22k-and-18k-gold/articleshow/60827424.cms|title=Purity of gold |work=The Times of India |date=15 April 2020 }}</ref> * 900—''one nine fine'': American Eagle denominations for 1837–1933; used in Latin Monetary Union mintage (e.g. French and Swiss "Napoleon coin" 20 francs). * 899—American Eagles briefly for 1834–1836. * 834—''20 karat'' * 750—''18 karat'': Typical fineness for modern jewelry in most of Europe.<ref name=Corti /> Even in regions where higher purities are common, this is the maximum fineness used for gemstone-set jewelry, as the metal must be hard enough to robustly hold the stone in place.<ref name="Purity of gold"/> * 625—''15 karat'' * 585—''14 karat'': Most common fineness for jewelry in the United States.<ref name=Corti>{{cite report |title=JEWELLERY ALLOYS – PAST, PRESENT and FUTURE |first=Christopher W |last=Corti |publisher=COReGOLD Technology |place=Reading Berks., UK |url=https://www.assayofficelondon.co.uk/media/2560/jewellery-alloys-past-present-future-c-corti.pdf | page=6}}</ref> While 14 karat is more precisely 583.3 fine, this level is not generally used in decimal fineness. * 500—''12 karat'' * 417—''10 karat'': Historically, the minimum standard for gold in the US. As of August 2018, any marked karat is permissible. * 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=https://spotgoldvalue.com/what-does-585-mean-on-gold-jewelry/ |title=What Does 585 Mean on Gold Jewelry? The Complete Guide |publisher= |access-date=2026-04-30 |url-status=live |archive-url= |archive-date= |website=SpotGoldValue}}</ref> It is also the minimum for Denmark, Greece and Mexico. * 042–''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=dead|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 nines fine'': ultra-fine silver used by the Royal Canadian Mint for their Silver Maple Leaf and other silver coins * 999—fine silver or three nines fine: Used in Good Delivery bullion bars and most silver bullion coins. Used in U.S. silver commemorative coins and silver proof coins starting in 2019.<ref>{{Cite web|url=https://www.coinworld.com/news/us-coins/coin_coinworld_300x600|title=U.S. Mint replaces 90 percent silver alloy with .999 fine silver|website=CoinWorld}}</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''<ref name="Silver standards" /> * 947.9: 91 zolotnik Russian silver<ref name="Silver standards" /> * 935: Swiss standard for watchcases after 1887, to meet the British 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. Used in the Art Deco period in Austria and Germany. Scandinavian silver jewelers used 935 silver after the 2nd World War.<ref name="Silver standards" /> * 933: Bolivian pesos bolivianos in 1975.<ref name=BoliviaMelt /> * 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). The standard used for English coinage from the time of Edward I <ref name="EB1911">{{cite EB1911 |wstitle= Sterling (money) |volume= 25 |page= 901 |short=1}}</ref> until 1920.<ref name="EB1911"/> Widely used in the manufacture of silver items, including flatware, jewelry, musical instruments, home decor, etc.<ref>{{Cite web|url=https://www.goldsilverbuffalo.com/resources/examples-of-items-in-your-home-that-may-contain-sterling-silver/|title=Examples of Items in Your Home That May Contain Sterling Silver}}</ref><ref name="Silver standards" /> * 917: a standard used for minting Indian silver (rupees), during the British raj and for some coins during the first Brazilian Republic. * 916: 88 zolotnik Russian silver (actually 91.66%)<ref name="Silver standards" /> * 903: Mexican Reals between 1823 and 1897 and Pesos 1910 to 1940;<ref name=MexicoMelt /> Bolivian Soles 1827–1859.<ref name=BoliviaMelt>{{Cite web|url=https://worldsilvermeltguide.com/europe/bolivia/|title=Bolivia Silver Coin Value|website=worldsilvermeltguide.com}}</ref> * 900: ''one 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 coins and silver proof coins 1982–2018. Also used in coins from Spain,<ref>{{cite web | title=5 Pesetas - Alfonso XIII, Spain | url=https://en.numista.com/4009 }}</ref> Russia,<ref>{{cite web | title=1 Rouble - Alexander III, Russian Empire | url=https://en.numista.com/24062 }}</ref> China, Argentina, Germany, Switzerland, Italy, Yugoslavia, Czechoslovakia, Hungary, Japan, Egypt, Turkey, Lebanon,<ref name="925-1000.com">{{cite web | title=Silver Standards of the World - Encyclopedia of Silver Marks, Hallmarks & Makers' Marks | url=https://www.925-1000.com/a_Standards.html }}</ref> Israel,<ref>{{cite web | title=10 Lirot, Israel | url=https://en.numista.com/31982 }}</ref> and Panama.<ref>{{cite web | title=1 Balboa, Panama | url=https://en.numista.com/9749 }}</ref> Commonly used in American cutlery before about 1870 <ref>{{Cite web|url=https://www.marthastewart.com/8104180/collecting-coin-silver-flatware|title=What Is Coin Silver Flatware and Is It Worth Anything Today?|website=Martha Stewart}}</ref> * 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.<ref name="Silver standards" /> Swiss standard, commonly used for export watchcases (also 800 and later 935). Also used in silver from the Baltic States, Finland, Poland, Switzerland, and Romania.<ref name="925-1000.com"/> Commonly found in jewelry and other silver items produced in the Soviet Union.<ref>{{cite web | title=What is 875 Silver? | date=13 August 2025 | url=https://nikolaroza.com/875-silver/ }}</ref> * 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;<ref name="Silver standards" /> 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. Some Bolivian centavos in 1909.<ref name=BoliviaMelt /> * 830: A common standard used in older Scandinavian silver<ref name="Silver standards" /><ref name=SwedenMelt /> * 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; Swedish silver;<ref name=SwedenMelt /> Canadian silver circulating coinage from 1920 to 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 dollars between 1965 and 1970, and commemorative issue Eisenhower dollars 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, Mexico,<ref name=MexicoMelt /> and Morocco. * 700: Chile 50 Centavos 1902–1905<ref name=ChileMelt /> * 600: Used in some examples of postwar Japanese coins, such as the 1957-1966 100 yen coin. Also used in older Swedish coins.<ref name=SwedenMelt>{{Cite web|url=https://worldsilvermeltguide.com/europe/sweden/|title=Sweden Silver Coin Melt Values|website=worldsilvermeltguide.com}}</ref> * 500: Standard used for British coinage 1920–1946 as well as Canadian circulating coins from 1967 to 1968 and commemoratives from 1971 to 1991 <ref>{{Cite web|url=https://goldadvert.com/knowledgebase/en/commemorative-silver-coins-of-canada/|title=Commemorative Silver Coins of Canada|date=November 1, 2018|website=Knowledge base - GoldAdvert}}</ref> and some coins from Colombia and Brazil. Also used on some Peruvian <ref>{{Cite web|url=https://worldsilvermeltguide.com/americas/peru/|title=Peru Silver Coin Melt Values|website=worldsilvermeltguide.com}}</ref> and Soviet <ref>{{Cite web|url=https://coin-identifier.com/catalog/russia/soviet-republic/silver|title=Silver Soviet Republic Coins from Russia: Value & Price Guide|website=Coin ID Scanner}}</ref> coins of the 1920s and 30s. Large Panamanian 20 balboas coins were also minted at this fineness from 1980 to 1985 <ref>{{Cite web|url=https://en.numista.com/catalogue/index.php?r=20+balboas|title=Search the catalogue – Numista|website=en.numista.com}}</ref> * 450: Chile Centavos 1915–1919<ref name=ChileMelt>{{Cite web|url=https://worldsilvermeltguide.com/americas/chile/|title=Chile Silver Coin Value|website=worldsilvermeltguide.com}}</ref> * 420: Used for Mexico 50 Centavos in 1935<ref name=MexicoMelt /> * 400: Some Swedish coins;<ref name=SwedenMelt /> early 1900s Chile centavos<ref name=ChileMelt /> * 350: Standard used for US Jefferson "war nickels" minted between 1942 and 1945. * 300: Used for Mexico 50 Centavos 1950–1951<ref name=MexicoMelt /> * 100: Used for Mexican pesos 1957–1967.<ref name=MexicoMelt>{{Cite web|url=https://worldsilvermeltguide.com/americas/mexico|title=Mexico Silver Coin Melt Values|website=worldsilvermeltguide.com}}</ref>

==<span class="anchor" id="Karat"></span><span class="anchor" id="Carat"></span><span class="anchor" id="carat"></span><span class="anchor" id="karat"></span> Carat== {{Redirect|Karat}} {{distinguish|text=Carat (mass), a unit of mass used for gemstones and pearls}}

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 ===

{{block indent|1=''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 Britain, 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-carat, 3-grain, 1-quart gold''.

The carat fractional system is increasingly being complemented or superseded by the 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 (nominally 58.33%) * 75.00–79.16% = 18 c (nominally 75.00%) * 91.66–95.83% = 22 c (nominally 91.66%) * 95.83–99.95% = 23 c (nominally 95.83%) * 99.95–100% = 24 c (nominally 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.

===Density===

To find approximate metal purity divide the weight of your metal (dry weight) by the weight after it's been submerged completely in water (wet weight) and check the density range.

<math display="block"> \frac { \text{DW}} { \text{WW}} = DR</math>

It is based on Archimedes' principle and the method he used in King Hiero II's crown. The metal must be completely submerged and held in place with a string or thread without touching the container.

{| class="wikitable" style="text-align:center" |+ Gold ! scope="col" rowspan="2" | Karat ! scope="col" rowspan="2" | Content ! scope="col" colspan="3" | Alloyed metal ! scope="col" rowspan="2" | Density range (±1%) |- ! scope="col" | Copper ! scope="col" | Copper and silver ! scope="col" | Silver |- | K24||1000/1000||colspan="3"| 19.32||19.31~19.51 |- | K22||916/1000||17.63||17.73||18.06||17.45~18.24 |- | K20||834/1000||16.19||16.42||16.94||16.03~17.11 |- | K18||750/1000||14.99||15.24||15.96||14.84~16.12 |- | K14||584/1000||13.04||13.38||14.30||12.91~14.44 |- | K10||417/1000||11.54||11.91||12.96||11.42~13.09 |}

===Etymology=== 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 {{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 {{lang|el-Latn|kerátion}} ({{lang|el|κεράτιον}}) meaning carob seed (literally "small horn")<ref name=harper>{{OEtymD|carat|accessdate=}}</ref><ref>Henry George Liddell, Robert Scott (1843). [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 }}. ''A Greek–English Lexicon'' – via Perseus Project at Tufts University.</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>Henry George Liddell, Robert Scott (1843). [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 }}. ''A Greek–English Lexicon'' – via Perseus Project at Tufts University.</ref>).

In 309{{spaces}}AD, Roman Emperor Constantine I began to mint a new gold coin, the ''solidus'', that was {{frac|72}} of a ''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 {{lang|la|siliquae}}, where each siliqua (or 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: 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 Britain was traditionally expressed as the mass of silver expressed in 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== * {{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 }} * [https://metalmetric.com/melt/gold/14k-gold-price-per-gram Live gold price per gram by karat] – Real-time melt value calculations for 10K through 24K gold using current spot prices

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

es:Ley (pureza)