Why is gold measured in Carats?

Hi,
Carat (ct) or Karat (Kt) [in the States and Canada it is Karat] is:
X = 24 * Xg / Xm    
X = the Karat value. 
Xg = the mass of the pure gold.
Xm = the total mass. 
According to that equation 24 Carat (Karat) is 100% pure (in fact 99.99%).  The reaso we use this term is simple convinience: In this way we can talk in simle small numbers: 12, 14, 18, 24.....  rather than saying 75% pure we say 18 karat. 
Best regards,

  4. Why is gold measured in carats?
This stems back to ancient times in the Mediterranean /Middle East, when a carat became used as a measure of the purity of gold alloys (see next Question 5). The purity of gold is now measured also in terms if fineness, i.e parts per thousand. Thus 18 carats is 18/24th of 1000 parts = 750 fineness.

Some sites you maybe interested in exploring are:

The site is: http://www.california-gold-rush-miner.us
 
 
Their museum nuggets are at:
http://www.california-gold-rush-miner.us/australia-gold-nuggets.htm
 
The most expensive gold is called Crystalline gold. Some great photos of it can be viewed at:
http://www.california-gold-rush-miner.us/crystalline-gold-miner.htm
http://california-gold-nuggets-miner.blogspot.com
http://www.brokerforyou.com/brokerforyou/
http://www.websitetrafficbuilders.com/adsense.htm
http://www.san-diego-dentist.us
http://www.medical-research-study-directory.info/san-diego-medical-research-study.htm
http://www.lasik-surgery-san-diego.info/lasik-eye-surgery-san-diego.htm

gold is usually combined with another metal.  Pure gold is 24kt gold.  So therefore, if you have 10kt gold, you have 10 parts gold, and 14 parts other metal (i.e. copper/nickel).

gold is usually combined with another metal.  Pure gold is 24kt gold.  So therefore, if you have 10kt gold, you have 10 parts gold, and 14 parts other metal (i.e. copper/nickel).

I hope someone has answered your question. I am going to add an article i wrote for a gold prospecting club's newsletter in the early 90's. I hope it helps you to understand gold a little better. Keep in mind that when you are using the formula to find your gold's value, that the spot gold price is no longer around $300, but more like $850.

Here it is:

1. Golds chemical symbol is au.
2. The total amount of gold mined in the u.S to date, would make a cube measuring a little more than 50 feet on each side.
3. One cubic foot of gold would weigh approx 14 hundred pounds or 1464.83 troy ounces
4. Golds specific gravity, a density measurement, is 19.3 this means an ounce of gold is 19.3 times heavier than an ounce of water.
5. Gold is very soft, measuring 2.5 on the mho scale, while talc measures at one and a diamond at 10.
Gold is very ductile and malleable, capable of one ounce being stretched for 60 miles, and gold leaf being flattened to 1/300 of an inch.
 
Karat mark/gold percent karat mark gold percent
10k .416
14k .585
18k .750
22k .916
24k 100% pure
 
To find gold content and dollar vaule use the following formula:
Karat divided by 24, multiplied by spot price, and divided by 20 equals the price per pennyweight.
Example: 14k divided by 24 equals .583
.583 multiplied by $363 (spot price) equals $212.80
$212.80 divided by 20 equals $10.64 (price per pennyweight)
Price per pennyweight multiplied by ring's weight (minus stones) is the scrap gold price for the ring
 
Gold in jewelry
Gold wash-----gold deposits with a thickness from 2 to 5 millionth of an inch
Gold plating-----deposits with a minimum thickness of 7 millionth of an inch
Gold inlays-----solid pieces of gold or gold alloy attached by dovetailing (usually 14-24 karat)
Gold leaf-----gold leaf is very thin, 3-4 millionth of an inch, made so by flattening under pressure. Can be hammered thin enough to transmit light
Gold filling-----refers to a base metal such as nickel that has gold sheet attached by soldering or some other means. Gold filled was once commonly used in watch cases
Heavy gold plate-----a film of fine gold plated to other metals to a thickness of at least 100 millionth of an inch.
 
Rolled gold-----a layer of plating, of 10 karat or better, mechanically bonded to a base metal. Gold content may be less then 1/20th total weight
 
Jewelry abbreviations
Gp-----gold plated
Gf-----gold filled
Hge-----heavy gold electroplate
14k-----ranges from 12k up
14kp-----14 plumb-----14/24 pure (.585 pure)
Plumb is used to guarantee gold content is not less than shown
Cubic zirconias are generally used in 10k jewelry
Diamonds are generally used in 14k and above
Some european countries use the number system in place of karats, thus, a ring marked .750 is 18 karat, one marked .585 is 14 karat, etc.