Carat (purity)

Carat (purity)

The karat or carat (symbol: K or kt) is a unit of purity for gold alloys.



Karat purity is measured as 24 times the purity by mass:

X = 24\,\frac{M_g}{M_m}


X is the karat rating of the material,
Mg is the mass of pure gold or platinum in the material, and
Mm is the total mass of the material.

Therefore, 24-Karat gold is fine (99.9% Au w/w), 18-Karat gold is 18 parts gold 6 parts another metal (forming an alloy), 12-Karat gold is 12 parts gold (12 parts another metal), and so forth.

In England, the Karat was divisible into four grains, and the grain was divisible into four quarts. For example, a gold alloy of \tfrac{381}{384} fineness (that is, 99.2% purity) could have been described as being 23-Karat, 3-grain, 1-quart gold.

The Karat system is increasingly being complemented or superseded by the millesimal fineness system, in which the purity of precious metals is denoted by parts per thousand of pure metal in the alloy.


"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 from Italian carato, which came from Arabic qīrāṭ (قيراط), which came from Greek kerátion (κεράτιον) meaning carob seed (literally "small horn")[1][2][3] (diminutive of κέρας - keras, "horn"[4]) and was a unit of weight[5] though it was not likely used to measure gold in classical times.[1]

In 309 CE, Roman Emperor Constantine I began to mint a new gold coin solidus that was 172 of a libra (Roman pound) of gold[6] equal to a mass of 24 siliqua, where each siliqua (or carat) was 11728 of a libra.[7] This is believed to be the origin of the value of the karat.[8]


22/22K - a quality mark indicating the purity of gold most popularly used in India. This purity was adapted and practiced by the big jewellers and was later passed to jewel smiths. The first 22 signifies the "Skin purity", the purity of the top layer of the gold jewelry, and the second 22 signifies that after melting purity of the gold jewellery will be 22-karat, or 91.67% of pure gold. This system is used to show consistency in the quality of the gold.

This practice was pioneered and introduced in the early mid-1980s by Nemichand Bamalwa & Sons of Kolkata, India, sparking a revolution[weasel words] in India, as it forced jewellers to indicate correctly the after-melting purity. Heightened consumer awareness made it a most sought-after stamp or quality mark.

This symbol or stamp can be found in Asian countries like India, Sri Lanka, Pakistan, Bangladesh, Nepal, Yemen, and Persian Gulf countries.

International caratages of gold jewellery

Region[9] Typical caratage (fineness)
Arabic countries, Far East (China, Hong Kong, Taiwan) 24-karat "Chuk Kam" (99.0% min)
Arabic countries, Bangladesh, India, Pakistan, and Sri Lanka 22-karat (91.6%)
Arabic countries in the Persian Gulf region 21-carat (87.5%), 18-karat (75.0%) in most Egypt
Europe - Southern / Portugal 19.2-karat (80.0%)
Europe - Southern / Mediterranean 18-karat (75.0%)
Europe - Northern Germany etc. 8- to 18-karat (33.3 - 75.0%)
Russia/former USSR 9- (37.5%) and 14-karat/old 583 and new 585 проба (58.5%)
United Kingdom 9-karat to 22 karat (37.5-91.6%)
United States 10-karat to 18-karat (41.7-75%)

Chuk Kam

Chuk Kam (足金) in Cantonese means pure gold, literally "exact gold". It is defined as 99.0% gold minimum with a 1.0% negative tolerance allowed.[9][10] The quality of gold is guaranteed with a "Certificate of Gold" upon purchases in Hong Kong and Macau. The related term "千足" and "万足" meaning "thousand exact" and "ten thousand exact" is also used for purity of 99.9% and 99.99% respectively. This is because the impurity is at most 1 in 1,000 in the case of 99.9% or 1 in 10,000 for 99.99%.

United States of America

The USA Federal Trade Commission (FTC) has standardized the karat markings used within its boundaries for almost 7 decades now[when?]. Under these regulations, items 10-karat or greater are to be stamped with either "K" or "Kt." Decimal markings are also an option under the CFTC regulations.

Under-karating is against the law in the United States of America. There are specific mandated consequences including fines, etc., based upon the severity of the infraction(s).

In addition, there is a set of tolerances to the required karat markings in the USA (always designated with a "K" and never a "C") depending upon the use of various soldering requirements when setting stones, mounting crowns, or creating prongs for 3 examples.[11]

See also

Gold alloys


  1. ^ a b Harper, Douglas. "carat". Online Etymology Dictionary. 
  2. ^ κεράτιον, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
  3. ^ Walter W. Skeat (1888), An Etymological Dictionary of the English Language
  4. ^ κέρας, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
  5. ^ carat, Oxford Dictionaries
  6. ^ Vagi, David L. (1999). Coinage and History of the Roman Empire. II: Coinage. Chicago: Fitzroy Dearborn. p. 100. ISBN 1-57958-316-4. Retrieved 18 November 2011. 
  7. ^ Grierson, Philip (1968). Catalogue of the Byzantine Coins in the Dumbarton Oaks Collection and in the Whittemore Collection. 2: pt. 1. Washington, DC: Dumbarton Oaks. p. 8. ISBN 0-88402-024-X. Retrieved 18 November 2011. 
  8. ^ Turnbull, L. A.; Santamaria, L.; Martorell, T.; Rallo, J.; Hector, A. (2006). "Seed size variability: From carob to carats". Biology Letters 2 (3): 397–400. doi:10.1098/rsbl.2006.0476. PMC 1686184. PMID 17148413.  edit
  9. ^ a b World Gold Council (2003)
  10. ^ Fallon, (2006)


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Carat — or karat may refer to:In the gem business: * Carat (mass), a unit of mass for gemstones, equal to 0.2 gram * Carat (purity) or karat, a unit of purity for goldIn entertainment: * Carat (board game), an abstract tile based German style board game… …   Wikipedia

  • Carat (mass) — This article is about the unit of mass used for gemstones and pearls. For the purity scale used for gold, see carat (purity). The carat is a unit of mass equal to 200 mg (0.2 g; 0.007055 oz) and is used for measuring gemstones and pearls.… …   Wikipedia

  • carat — (n.) mid 15c., from M.Fr. carat measure of the fineness of gold (14c.), from It. carato, from Arabic qirat pod, husk, weight of 4 grains, from Gk. keration carob seed, lit. little horn dim. of keras horn (see KERATO (Cf. kerato )). Carob beans… …   Etymology dictionary

  • carat — carat, caret Carat (AmE karat) is a measure of the purity of gold; caret is a mark (λ) for showing an insertion in printing or writing …   Modern English usage

  • carat — ► NOUN 1) a unit of weight for precious stones and pearls, equivalent to 200 milligrams. 2) (US also karat) a measure of the purity of gold, pure gold being 24 carats. ORIGIN French, from Greek keration fruit of the carob (also denoting a unit of …   English terms dictionary

  • carat — (ct or c)    1. a unit of mass used for diamonds and other precious stones. Originally spelled karat, the word comes from the Greek keration, a carob bean; carob beans were used as standards of weight and length in ancient Greece in much the same …   Dictionary of units of measurement

  • carat — 1) A measure of the purity (fineness) of gold. Pure gold is defined as 24 carat; 14 carat gold contains 14 24ths gold, the remainder usually being copper. 2) A unit for measuring the weight of a diamond or other gemstone, equal to 0. 2 gram …   Big dictionary of business and management

  • carat —  , caret, karat  A carat is the unit of measurement used by jewelers; a caret is an insertion mark (^) associated with proofreading; a karat is a measure of the purity of gold …   Bryson’s dictionary for writers and editors

  • carat — [ karət] noun 1》 a unit of weight for precious stones and pearls, equivalent to 200 milligrams. 2》 (US also karat) a measure of the purity of gold, pure gold being 24 carats. Origin ME: from Fr., from Ital. carato, from Arab. ḳīrāṭ, from Gk… …   English new terms dictionary

  • carat — /kaerat/ A measure of weight for diamonds and other precious stones, equivalent to three and one sixth grains Troy, though divided by jewelers into four parts called diamond grains. Also a standard of fineness of gold, twenty four carats being… …   Black's law dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.