The carat is a unit of mass used for measuring gems and pearls, and is exactly 200 milligrams.^[1] The word came to English from French, derived from the Greek kerátion (κεράτιον), “fruit of the carob”,^[2] via Arabic qīrāṭ (قيراط) and Italian carato. Carob seeds were used as weights on precision scales because of their reputation for having a uniform weight. However, a 2006 study^[3] found carob seeds to have as much variation in their weights as do other seeds, though it seems that it is easier than with other seeds to recognize particularly large or small specimens and remove them.^[4] Thus, the carob seed was used as a weight not because it was naturally more uniform in weight, but because it could be more easily standardized. For other uses, see Mass (disambiguation). ... For other uses, see Gemstone (disambiguation). ... For other uses, see Pearl (disambiguation). ... The milligram (symbol mg) is an SI unit of mass. ... Binomial name Linnaeus The Carob tree (from Arabic: خروب kharoub and Hebrew: חרוב Charuv), Ceratonia siliqua, is an evergreen shrub or tree native to the Mediterranean region, cultivated for its edible seed pods. ... Arabic is a Semitic language, closely related to Hebrew and Aramaic. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... For other uses, see Natural selection (disambiguation). ...

In past centuries, different countries each had their own carat unit, all roughly equivalent to the mass of a carob seed. In the United Kingdom, before 1888, the Board of Trade carat was exactly grains;^[5] after 1887, the Board of Trade carat was exactly grains.^[6] Despite it being a non-metric unit, a number of metric countries used this unit for its limited range of application. In 1907, the definition of the metric carat of 200 milligrams was adopted at the Fourth General Conference on Weights and Measures; this replaced the non-metric carat definition in the United States on July 1, 1913, and superseded the Board of Trade carat in the United Kingdom on 1 April 1914. The metric carat is the one that is universally used today. For the toll-free telephone number see Toll-free telephone number Year 1888 (MDCCCLXXXVIII) was a leap year starting on Sunday (click on link for calendar) of the Gregorian calendar (or a leap year starting on Friday of the 12-day slower Julian calendar). ... A grain is a unit of mass equal to 0. ... 1887 (MDCCCLXXXVII) is a common year starting on Saturday (click on link for calendar) of the Gregorian calendar or a common year starting on Monday of the Julian calendar. ... The Board of Trade circa 1808. ... Year 1907 (MCMVII) was a common year starting on Tuesday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Monday of the 13-day-slower Julian calendar). ... The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures (CGPM, never GCWM). ... is the 182nd day of the year (183rd in leap years) in the Gregorian calendar. ... Year 1913 (MCMXIII) was a common year starting on Wednesday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Tuesday of the 13-day-slower Julian calendar). ... is the 91st day of the year (92nd in leap years) in the Gregorian calendar. ... Year 1914 (MCMXIV) was a common year starting on Thursday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Wednesday of the 13-day-slower Julian calendar). ...

The carat is divisible into one hundred points of two milligrams each. The Board of Trade carat was divisible into four diamond grains,^[7] but measurements were typically made in multiples of carat.

There were also two varieties of refiners’ carats once used in the United Kingdom — the pound carat and the ounce carat.^[8] The pound troy was divisible into 24 pound carats of 240 grains troy each; the pound carat was divisible into four pound grains of 60 grains troy each; and the pound grain was divisible into four pound quarters of 15 grains troy each. Similarly, the ounce troy was divisible into 24 ounce carats of 20 grains troy each; the ounce carat was divisible into four ounce grains of 5 grains troy each; and the ounce grain was divisible into four ounce quarters of 1¼ grains troy each.^[9] The pound or pound-mass (abbreviations: lb, , lbm, or sometimes in the United States: #) is a unit of mass (sometimes called weight in everyday parlance) in a number of different systems, including the imperial and US and older English systems. ... This article is about Ounce (unit of mass). ...

For diamonds, a paragon is a flawless stone of at least 100 carats (20 g). This article is about the mineral. ... BIC pen cap, about 1 gram. ...

The ANSI X.12 EDI standard abbreviation for the carat is CD. The American National Standards Institute or ANSI (pronounced an-see) is a nonprofit organization that oversees the development of standards for products, services, processes and systems in the United States. ... An inter-company, application-to-application communication of data in standard format for business transactions Electronic Data Interchange (EDI) is a set of standards for structuring information that is to be electronically exchanged between and within businesses, organizations, government entities and other groups. ...

Notes and references

1. ^ Two hundred milligrams is approximately grains.
2. ^ The literal translation of κεράτιον is little horn, which describes the seed pod.
3. ^ Turnbull, Lindsay, et al. “Seed size variability: from carob to carats”
4. ^ “Did carob seeds allow shady diamond deals?”, New Scientist, page 20, 6 May 2006.
5. ^ The pre-1888 Board of Trade carat, of which there were exactly per ounce troy, was approximately 205.4094 mg.
6. ^ The post-1887 Board of Trade carat, of which there were exactly 151½ per ounce troy, was approximately 205.3035 mg.
7. ^ Unlike the modern carat, the Board of Trade carat was not used for measuring pearls; those were measured with pearl grains.
8. ^ The refiners’ carats were the offspring of the carat as a measure of fineness for gold.
9. ^ Chaffers, William. 1883. Hall Marks on Gold and Silver Plate. 6^th edition. London: Bickers & Son.

A grain is a unit of mass equal to 0. ... New Scientist is a weekly international science magazine covering recent developments in science and technology for a general English-speaking audience. ... is the 126th day of the year (127th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... The Board of Trade circa 1808. ... This article is about Ounce (unit of mass). ... Carat is a measure of the purity of gold and platinum alloys. ... Year 1883 (MDCCCLXXXIII) was a common year starting on Monday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Saturday of the 12-day slower Julian calendar). ... This article is about the capital of England and the United Kingdom. ...

External links

• A chart showing the size of various round diamond carat weights.
• A PDF chart showing the size of various fancy shaped diamond carat weights.