Gold purity is the most important and relevant parameter for Gold jewellary.Purity is described in the units of carat or Karat. karat purity is measured as :
Karat purity= 24 x (Mass of Pure Gold/The total mass of material)
Therefore for 24-karat gold purity comes to be 99.99%.
For 22-karat gold purity comes to be 0.9166 or 91.66%.It means that my 22 carat gold jewellary carries 91.66% pure gold and remaining alloying material or impurities.
18-carat gold contains only 75% pure gold and remaining 25% impurities.
Which are commonly used alloying materials:
Commonly used impurities are copper,nickel and zinc.
Gold naturally do not carry ductile properties so it needs to be alloyed with ductile metal like copper.Its not possilble to make jewellary of pure gold as it can break very easily.
There is one more method known as ”Fitness” to judge the purity of gold.In fitness system,purity of gold is denoted by parts per thousand of pure metal in the alloy.
Thus for 18 carat = 18/24 of 1000 parts
= 0.75 x 1000
= 750 fitness.
Gold traded at different exchanges in India like Multi-commodity exchange,ICEX or national Spot exchange is of 99.9 purity for buyers while accepted gold quaility is minimum 99.5 for sellers.
While buying gold,one needs to ascertain the purity factor.Certification by independant agency like Hallmark or mark of 22/22k may be considered for safety purpose.
