Carats vs Karats
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-Carat (kret) 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 quartus, from Arabic qrt, 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 (kret) 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 Concice Etymological Dictionary of the English Language, Skeat, Capricorn Books, 1963

-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
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
from Gemstone and Mineral Data Book, John Sinkankas, Van Nostrand Pub., 1981
-Gem Cuts
Formulas for weights of various gem cuts, with dimensional ratios
-Formulas
So-called "Standard Formulas" for computing the volume of various gem cuts, sort of a starting point for the Dendritics Automated Calculations algorithms.

 

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