Carats vs Karats

Carat (kàr´et) noun: 1. Abbr. c, car.. A unit of weight for precious stones, equal to 200 milligrams.; 2. Variant of KARAT.; [Middle English, from Old French, from Medieval Latin quarâtus, from Arabic qìrât, weight of four grains, from Greek keration, a weight, diminutive of keras, horn.]
Webster Definition for carat: 1. carat var of KARAT; 2. car.at \'kar-*t\ n [prob. fr. ML carratus, fr. Ar qi-ra-t bean pod, a small weight, fr. Gk keration carob bean, a small weight, fr. dim. of kerat-, keras horn : a unit of weight for precious stones equal to 200 milligrams
Karat also carat (kàr´et) noun: Abbr. k, kt.; A unit of measure for the fineness of gold, equal to 1/24 part. Pure gold is 24 karat; gold that is 50 percent pure is 12 karat.; [Variant of CARAT.]
Carat (F.-Ital.-Arab.-Gk): F. carat, a very light weight.; Ital. carato.; Arab. qirrat, a pod, husk, carat, 24th part of an ounce.; Gk. kepatiov, fruit of the locust-tree; also, a carat; lit. 'a small horn'; Gk. kepas, stem of , a horn; See Horn.; A Concise Etymological Dictionary of the English Language, Skeat, Capricorn Books, 1963 (My embarrassing misspelling corrected by Professor Nick Humez)
Carat weight: The unit of weight for diamonds and gemstones. It is defined as one-fifth of a gram (200 milligrams = 0.200 gram). It became legal standard on the 1st of April, 1914, and was and frequently still is, known as the metric carat. The old London carat weighed 0.20530 gram, and was not a legal standard and did not conform to the carat weight in other parts of the world, which varied in different countries from 0.1885 gram to 0.2135 gram.; Glossary, Gemmologists' Compendium (6 edition), Robert Webster FGA, revised by E. Allan Jobbins BSc, CEng, FIMM, FGA, Keeper of Minerals and Gemstones at the Institute of Geological Sciences (The Geological Museum), London, 1979.
Weights of carats (in milligrams) before standardization on the metric carat of 200.0 mg

Formulas: So-called "Standard Formulas" for computing the volume of various gem cuts, sort of a starting point for the Dendritics Automated Calculations algorithms.

Alexandria	191.7 mg	Frankfurt	205.8 mg
Amsterdam	205.1 mg	Hamburg	205.8 mg
Antwerp	205.3 mg	Lisbon	205.8 mg
Arabia	194.4 mg	London	205.3-205.5 mg
Austria-Hungary	206.1 mg	Madras	205.5 mg
Berlin	205.5 mg	Persia	213.5 mg
Bologna	188.5 mg	Russia	205.1 mg
Brazil	192.2 mg	Spain	199.9 mg
Constantinople	205.5 mg	Turin	213.5 mg
East Indies	196.9-205.5 mg	Venice	207.0 mg
Florence	196.5 mg	Vienna	206.1 mg
France	205.0-205.5 mg	Pearl Carat	207.3 mg