gold details

24 Carat (Karat) is a pure Gold. It doesn’t use for any Jewelry or coins because gold is an extremely soft metal which loses particles if used or handled a lot, so other metals have to be added to strengthen it before it can be made into jewelry or coins.

Which metals are they use for strengthen and why?

Copper, Silver and Zinc are the metals they use for strengthen purpose.

Metal proportion

22 carat Gold (Au Chemical symbol) = 91.6% + 8.4% (Silver or Copper).

18 carat Gold = 75% (Au) + 21% (Copper) + 4% (Silver). (For holding gemstones such as diamonds and emerald in place).

14 carat Gold = 58.3% (Au) + 41.36% (others).

9 carat Gold = 37.5% (Au) +62.5 (others).

Calculation

22 carat gold is 91.6% Au. Divide the mass by 24, then 22/24 parts of it by mass are pure gold. Other 2 carats are made from Silver or Copper.  

Color

22 carat tends to look a shiny yellow. How shiny is depends up on other metal like as copper or silver, mainly copper has a slightly redder tint so Zinc is added to the copper to neutralize the rose color and make it more yellow.

18 carat is 18/24. If copper is 25% material color is Rose.

                                 If 21% copper + 4% silver material color is Pink.

14 carat is 14/24.           

                                        

9 carat is 9/24. Other alloy is Copper it looks like a dull bronze color sometimes green or black. If other metal in the alloy is silver or nickel it looks like white (white gold is made with silver because European restrict the use of nickel in jewelry, it causes skin problems.)

Finally

The best quality 22 carat gold is alloyed with silver and it is the most expensive.

Sometimes we see hallmark rate on gold “916”, which denotes it is 91.6% pure gold in it. Sometimes the hallmark will just say “22” to denote the carat.