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The fineness of a
precious metal Precious metals are rare, naturally occurring metallic chemical elements of high economic value. Chemically, the precious metals tend to be less reactive than most elements (see noble metal). They are usually ductile and have a high lus ...
object (coin, bar, jewelry, etc.) represents the weight of ''fine metal'' therein, in proportion to the total weight which includes
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...
ing
base metal A base metal is a common and inexpensive metal, as opposed to a precious metal such as gold or silver. In numismatics, coins often derived their value from the precious metal content; however, base metals have also been used in coins in the pa ...
s and any
impurities In chemistry and materials science, impurities are chemical substances inside a confined amount of liquid, gas, or solid, which differ from the chemical composition of the material or compound. Firstly, a pure chemical should appear thermodyn ...
. Alloy metals are added to increase
hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...
and durability of
coins A coin is a small, flat (usually depending on the country or value), round piece of metal or plastic used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in large quantities at a mint in order ...
and
jewelry Jewellery ( UK) or jewelry ( U.S.) consists of decorative items worn for personal adornment, such as brooches, rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the clothes. From a we ...
, alter colors, decrease the cost per weight, or avoid the cost of high-purity refinement. For example,
copper Copper is a chemical element with the Symbol (chemistry), symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductility, ductile metal with very high thermal conductivity, thermal and electrical conductivity. A fre ...
is added to the precious metal
silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
to make a more durable alloy for use in coins, housewares and jewelry. Coin silver, which was used for making
silver coin Silver coins are considered the oldest mass-produced form of coinage. Silver has been used as a coinage metal since the times of the Greeks; their silver drachmas were popular trade coins. The ancient Persians used silver coins between 612–3 ...
s in the past, contains 90% silver and 10% copper, by
mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementa ...
.
Sterling silver Sterling silver is an alloy of silver containing 92.5% by weight of silver and 7.5% by weight of other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925. '' Fine silver'', which is 99.9% pure silver, i ...
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 and '' karats'' or ''carats'' used only for
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile meta ...
. Karats measure the parts per 24, so that 18 karat = = 75% and 24 karat gold is considered 100% gold.

# Millesimal fineness

Millesimal fineness is a system of denoting the purity of
platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Pla ...
,
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile meta ...
and
silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...
s 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 "14K", "18K", 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 A hallmark is an official mark or series of marks struck on items made of metal, mostly to certify the content of noble metals—such as platinum, gold, silver and in some nations, palladium. In a more general sense, the term '' hallmark'' can ...
, and the fineness may vary slightly from the traditional versions of purity. Here are the most common millesimal finenesses used for
precious metal Precious metals are rare, naturally occurring metallic chemical elements of high economic value. Chemically, the precious metals tend to be less reactive than most elements (see noble metal). They are usually ductile and have a high lus ...
s and the most common terms associated with them.

## Platinum

* 999.5: 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 * 925 * 900—''one nine fine'' * 850 * 750

## Gold

* 999.999—''six nines fine'': The purest gold ever produced. Refined by the
Perth Mint The Perth Mint is Australia's official bullion mint and wholly owned by the Government of Western Australia. Established on 20 June 1899, two years before Australia's Federation in 1901, the Perth Mint was the last of three Australian colo ...
in 1957. * 999.99—''five nines fine'': The purest type of gold currently produced; the
Royal Canadian Mint }) is the mint of Canada and a Crown corporation, operating under the ''Royal Canadian Mint Act''. The shares of the Mint are held in trust for the Crown in right of Canada. The Mint produces all of Canada's circulation coins, and manufacture ...
regularly produces commemorative coins in this fineness, including the world's largest at 100 kg. * 999.9—''four nines fine'': Most popular. E.g. ordinary
Canadian Gold Maple Leaf The Canadian Gold Maple Leaf (GML) is a gold bullion coin that is issued annually by the Government of Canada. It is produced by the Royal Canadian Mint. The Gold Maple Leaf is legal tender with a face value of 50 Canadian dollars. The market ...
and American Buffalo coins * 999—''24 karat'', also occasionally known as ''three nines fine'': e.g.,
Chinese Gold Panda The Chinese Gold Panda () is a series of gold bullion coins issued by the People's Republic of China. The Official Mint of the People's Republic of China introduced the panda gold bullion coins in 1982. The panda design changes every year (with ...
coins * 995: The minimum allowed in Good Delivery gold bars * 990—''two nines fine'' * 986—''
Ducat The ducat () coin was used as a trade coin in Europe from the later Middle Ages from the 13th to 19th centuries. Its most familiar version, the gold ducat or sequin containing around of 98.6% fine gold, originated in Venice in 1284 and gained ...
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 Eagle is the common name for many large birds of prey of the family Accipitridae. Eagles belong to several groups of genera, some of which are closely related. Most of the 68 species of eagle are from Eurasia and Africa. Outside this area, ju ...
denominations from 1795–1833. Currently used for British Sovereigns, South African Krugerrands, and the modern (1986—present)
American Gold Eagle The American Gold Eagle is an official gold bullion coin of the United States. Authorized under the Gold Bullion Coin Act of 1985, it was first released by the United States Mint in 1986. Because the term "eagle" also is the official United ...
s. * 900—''one nine fine'': American Eagle denominations for 1837–1933; currently used in
Latin Monetary Union The Latin Monetary Union (LMU) was a 19th-century system that unified several European currencies into a single currency that could be used in all member states when most national currencies were still made out of gold and silver. It was establ ...
mintage (e.g. French and Swiss " 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 USA * 375—''9 karat'' * 333—''8 karat'': Minimum standard for gold in Germany after 1884

## Silver

* 999.99—''five nines fine'': The purest silver ever produced. This was achieved by the Royal Silver Company of Bolivia. * 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 current silver bullion coins. Used in U.S. silver
commemorative coin Commemorative coins are coins issued to commemorate some particular event or issue with a distinct design with reference to the occasion on which they were issued. Many coins of this category serve as collectors items only, although some countries ...
s and silver
proof coin Proof coinage refers to special early samples of a coin issue, historically made for checking the dies (as in demonstrating that something is true) and for archival purposes. Nowadays proofs are often struck in greater numbers specially for ...
s starting in 2019. * 980: common standard used in Mexico ca. 1930–45 * 958: () '' Britannia silver'' * 950: ''French 1st Standard'' * 947.9: 91 zolotnik Russian silver * 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. * 935: used in the Art Deco period in Austria and Germany. Scandinavian silver jewellers used 935 silver after the 2nd World War * 925: () ''
Sterling silver Sterling silver is an alloy of silver containing 92.5% by weight of silver and 7.5% by weight of other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925. '' Fine silver'', which is 99.9% pure silver, i ...
'' 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 Rupee is the common name for the currencies of India, Mauritius, Nepal, Pakistan, Seychelles, and Sri Lanka, and of former currencies of Afghanistan, Bahrain, Kuwait, Oman, the United Arab Emirates (as the Gulf rupee), British East Afr ...
), during the British raj and for some coins during the first Brazilian Republic. * 916: 88 zolotnik Russian silver * 900: ''one
nine 9 is a number, numeral, and glyph. 9 or nine may also refer to: Dates * AD 9, the ninth year of the AD era * 9 BC, the ninth year before the AD era * 9, numerical symbol for the month of September Places * Nine, Portugal, a parish in the ...
fine'', ''coin-silver'' , or ''90% silver'': e.g.
Flowing Hair Flowing Hair coinage was issued in the United States between 1793 and 1795. The design was used for the first half dime, half dollar, dollar, and the first two large cents. Flowing Hair coins ''Source:'' * Silver center cent (1792) * Chain ...
and 1837–1964 U.S. silver coins. Also used in U.S. silver
commemorative coin Commemorative coins are coins issued to commemorate some particular event or issue with a distinct design with reference to the occasion on which they were issued. Many coins of this category serve as collectors items only, although some countries ...
s and silver
proof coin Proof coinage refers to special early samples of a coin issue, historically made for checking the dies (as in demonstrating that something is true) and for archival purposes. Nowadays proofs are often struck in greater numbers specially for ...
s 1982–2018. * 892.4: US coinage 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). * 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 The Latin Monetary Union (LMU) was a 19th-century system that unified several European currencies into a single currency that could be used in all member states when most national currencies were still made out of gold and silver. It was establ ...
* 833: () 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 * 750: an uncommon silver standard found in older German, Swiss and
Austro-Hungarian Austria-Hungary, often referred to as the Austro-Hungarian Empire,, the Dual Monarchy, or Austria, was a constitutional monarchy and great power in Central Europe between 1867 and 1918. It was formed with the Austro-Hungarian Compromise ...
silver * 720: Decoplata :many Mexican and Dutch silver coins use this standard, as well as some coins from Portugal's former colonies, Japan, Uruguay, Ecuador, Egypt, and Morocco. * 600: Used in some examples of postwar Japanese
coins A coin is a small, flat (usually depending on the country or value), round piece of metal or plastic used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in large quantities at a mint in order ...
, such as the 1957-1966
100 yen coin The is a denomination of Japanese yen. The current design was first minted in silver in 1959 and saw a change of metal in 1967. It is the second-highest denomination coin in Japan after the 500 yen coin. The current 100 yen coin is one of two ...
* 500: Standard used for making British coinage 1920–1946 as well as Canadian coins from 1967-1968, and some coins from Colombia and Brazil. * 400: Standard used for US half dollars between 1965 and 1970, and commemorative issue
Eisenhower dollar The Eisenhower dollar was a one-dollar coin issued by the United States Mint from 1971 to 1978; it was the first coin of that denomination issued by the Mint since the Peace dollar series ended in 1935. The coin depicts President Dwight D. ...
s between 1971 and 1978. Also used in some Swedish Krona coins. * 350: Standard used for US Jefferson 'War Nickels' minted between 1942 and 1945.

# Karat

The karat (US spelling, symbol K or kt) or carat (UK spelling, symbol C or ct) is a fractional measure of purity for
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile meta ...
alloys An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...
, in parts fine per 24 parts whole. The karat system is a standard adopted by US federal law.

## Mass

:''K'' = 24 × ''M''g / ''M''m where : ''K'' is the karat rating of the material, : ''M''g is the mass of pure gold in the alloy, and : ''M''m is the total mass of the material. 24-karat gold is pure (while 100% purity is unattainable, this designation is permitted in commerce for 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. 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-karat, 3-grain, 1-quart gold''. The karat fractional system is increasingly being complemented or superseded by the millesimal system, described above. Conversion between percentage of pure gold and karats: * 58.33–62.50% = 14K (acclaimed 58.33%) * 75.00–79.16% = 18K (acclaimed 75.00%) * 91.66–95.83% = 22K (acclaimed 91.66%) * 95.83–99.95% = 23K (acclaimed 95.83%) * 99.95–100% = 24K (acclaimed 99.95%)

## Volume

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 metal(s). The quantity of gold ''by volume'' in a less-than-24-karat gold alloy differs according to the alloy(s) 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. This formula gives the amount of gold in cubic centimeters or in milliliters in an alloy: : $V_\text = \frac$ where : ''V''Au is the volume of gold in cubic centimeters or in milliliters, : ''M''a is the total mass of the alloy in grams, and : ''kt'' is the karat purity of the alloy. To have the percentage of the volume of gold in an alloy, divide the volume of gold in cubic centimetres or in millilitres by the total volume of the alloy in cubic centimetres or in millilitres. For 10-carat gold, the gold volume in the alloy represents about 26% of the total volume for standard yellow gold. Talking about purity according to mass could lead to some misunderstandings; for many people, purity means volume.

## Etymology

''Karat'' is a variant of ''carat''. First attested in English in the mid-15th century, the word ''carat'' came from
Middle French Middle French (french: moyen français) is a historical division of the French language that covers the period from the 14th to the 16th century. It is a period of transition during which: * the French language became clearly distinguished from t ...
, in turn derived either from Italian or Medieval Latin . These were borrowed into Medieval Europe from the
Arabic Arabic (, ' ; , ' or ) is a Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C. E.Watson; Walter ...
meaning "fruit of the carob tree", also "weight of 5 grains", () and was a unit of mass though it was probably not used to measure gold in classical times. The Arabic term ultimately originates from the
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
() meaning
carob The carob ( ; ''Ceratonia siliqua'') is a flowering evergreen tree or shrub in the Caesalpinioideae sub-family of the legume family, Fabaceae. It is widely cultivated for its edible fruit pods, and as an ornamental tree in gardens and landscap ...
seed (literally "small horn") (diminutive of – , "horn"). In 309 CE, Roman Emperor
Constantine I Constantine I ( , ; la, Flavius Valerius Constantinus, ; ; 27 February 22 May 337), also known as Constantine the Great, was Roman emperor from AD 306 to 337, the first one to convert to Christianity. Born in Naissus, Dacia Mediterran ...
began to
mint MiNT is Now TOS (MiNT) is a free software alternative operating system kernel for the Atari ST system and its successors. It is a multi-tasking alternative to TOS and MagiC. Together with the free system components fVDI device drivers, XaAES ...
a new gold coin ''
solidus Solidus (Latin for "solid") may refer to: * Solidus (coin) The ''solidus'' (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect sp ...
'' that was of a ''
libra Libra generally refers to: * Libra (constellation), a constellation * Libra (astrology), an astrological sign based on the star constellation Libra may also refer to: Arts and entertainment * ''Libra'' (novel), a 1988 novel by Don DeLillo Mus ...
'' (Roman pound) of gold equal to a mass of 24 ''
siliqua The siliqua (plural ''siliquae'') is the modern name given (without any ancient evidence to confirm the designation) to small, thin, Roman silver coins produced in the 4th century A.D. and later. When the coins were in circulation, the Latin wo ...
e'', where each siliqua (or carat) was of a libra. This is believed to be the origin of the value of the karat.

# 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 X-ray fluorescence (XRF) is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by being bombarded with high-energy X-rays or gamma rays. The phenomenon is widely used for elemental analysis ...
(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.

# Fine weight

A piece of
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...
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 Troy weight is a system of units of mass that originated in 15th-century England, and is primarily used in the precious metals industry. The troy weight units are the grain, the pennyweight (24 grains), the troy ounce (20 pennyweights), an ...
of 18 karat gold (which is 75% gold) may be said to have a fine weight of 0.75 troy ounces.

# Troy mass of silver content

Fineness of silver in
Britain Britain most often refers to: * The United Kingdom, a sovereign state in Europe comprising the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands * Great Britain, the largest island in the United King ...
mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementa ...
of silver expressed in troy ounces and pennyweights ( 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 $\frac = 95.833\%$ silver, whereas
sterling silver Sterling silver is an alloy of silver containing 92.5% by weight of silver and 7.5% by weight of other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925. '' Fine silver'', which is 99.9% pure silver, i ...
has a fineness of 11 ounces, 2 pennyweights, or exactly $\frac = 92.5\%$ silver.

* Colored gold *
Electrum Electrum is a naturally occurring alloy of gold and silver, with trace amounts of copper and other metals. Its color ranges from pale to bright yellow, depending on the proportions of gold and silver. It has been produced artificially, and ...
*
Gold as an investment Of all the precious metals, gold is the most popular as an investment. Investors generally buy gold as a way of diversifying risk, especially through the use of futures contracts and derivatives. The gold market is subject to speculation ...
*
Gold coin A gold coin is a coin that is made mostly or entirely of gold. Most gold coins minted since 1800 are 90–92% gold (22 karat), while most of today's gold bullion coins are pure gold, such as the Britannia, Canadian Maple Leaf, and American B ...
* Platinum coin * Silver as an investment *
Silver coin Silver coins are considered the oldest mass-produced form of coinage. Silver has been used as a coinage metal since the times of the Greeks; their silver drachmas were popular trade coins. The ancient Persians used silver coins between 612–3 ...
*
Tumbaga ''Tumbaga'' is the name for a non-specific alloy of gold and copper given by Spanish Conquistadors to metals composed of these elements found in widespread use in pre-Columbian Mesoamerica in North America and South America. The term is believe ...