As appearing in The Gold Nugget, April 1997
Submitted by Ken Oyler
Last updated: 24 JUN 2004
Carat vs. Karat
A carat is a unit of weight for precious stones, equal to 1/5 gram or 200 milligrams. It is also a 24th part of gold in an alloy. A karat is defined similarly, so they are in fact the same.
The only apparent difference is in their use. Carat is normally associated with precious gemstones, whereas karat is associated with gold. The abbreviation K stems from its French origin.
24 Karat is 100% pure (1.000 Fine)
18 Karat is 75% pure (.7500 Fine)
14 Karat is 58% pure (.5883 Fine)
12 Karat is 50% pure (.5000 Fine)
10 Karat is 42% pure (.4167 Fine)
8 Karat is 33% pure (.3323 Fine)
U.S. Gold Coins are 22 K (.9166 Fine)
Laboratory Pure Gold is 1.000 Fine
Commercially Fine Gold is .999 Fine
The weight of gold is determined in the scale of troy ounces rather than the avoirdupois scale.
Their commonality is in grains: there are 480 grains in one troy ounce, 437.5 grains in one avoirdupois ounce.
Abbreviations: Pennyweight = dwt, ounce = oz., troy = t, and avoirdupois = av.
To convert avoirdupois ounces to troy ounces, multiply by .9114883.
1 oz. (t) = 20 dwt (Pennyweight), 31.1035 grams, 480 grains, 1.0971 oz. (av)
1 dwt = 1.55517 grams, 24 grains, 0.05486 oz. (av)
1 gram = .64301 dwt, 15.432 grains, 0.03215 oz. (t), 0.03527 oz. (av)
A nugget is a piece of native gold larger than one troy grain in weight.
The Alchemists' Crucible
Symbol - Au
Atomic number - 79
Atomic weight - 196.97
Melting point - 1063 °C (1945 °F)
Specific Gravity - 19.32
Hardness (MOHS Scale) - 2.5 to 3.0