ABOUT THE GOLD

For the past several years, the brilliant luster of Gold has fascinated many. Since it was first found it has been a part of our lives. To a lot of people Gold has not just been a precious metal but an investment as well. Since the stone age as estimated 1,30,000 tones of gold has been produced, over half of which has been mined since 1850.

It may sound surprising but it is true that as many as 17 tones of ore is mined to extract a single ounce (31.104gm) of gold. Gold is available from earth’s crust, in the seas, river and plants. In nature gold if found in veins and secondary alluvial deposits as a free metal or in combined state. Gold is also recovered as byproduct from Silver & Copper refining.

Placer mining or panning and open pit mining is techniques commonly used to recover gold from earth. South Africa is world’s single largest gold producer, followed by USA, Australia, Russia and Canada and West Africa.
 

Physical and Chemical Properties of Noble Metals

Metal Name

Chemical Symbol

Color

Melting Point

Density

Gold

Au

Yellow

1064 C

19.32

Silver

Ag

White

962 C

10.56

Platinum

Pt

White

1773 C

21.45

 

Purity Standards

Percent Gold

European System

Karat System

100  %

999 Fine

24 K

95.83%

958 Fine

23 K

91.6 %

916 Fine

22 K

87.6 %

875 Fine

21 K

75.0 %

750 Fine

18 K

58.3 %

583 Fine

14 K

37.5 %

375 Fine

9 K

Percent   : Parts of gold per 100

Fineness : Parts of gold per 1000

Karat       : Parts of gold per 24

NOTE : Karat not to be confused with CARAT, which is used to state the weight of a gemstone. However in INDIA carat normally defines fineness of gold.

Effect of Acid on Metals:

1.      Gold: NO single acid can dissolve or attack directly except in presence of oxidizing agent.

2.      Gold will dissolve in Aquaregia (1 part of Nitric Acid and 4 parts of Hydrochloric Acid)

3.      Gold will dissolve in Potassium Cyanide in presence of oxidizing agent.

4.      An alloy of silver, copper or zinc will attack gold.

5.      Silver will dissolve in Nitric Acid.

6.      Platinum is almost resistance to any acid.

Gold and Platinum have no weather effect. In other words gold and platinum do not rust, tarnish or get corroded. While in case of Silver it will be effected by atmospheric pollution.
 
The typical composition of 23, 22, 21, 18, 14 and 9 carat yellow, red and white gold alloys.

 

Typical Composition of Yellow Gold Alloys

Grades in Carat

Metals, Percent by Mass

Au

Ag

Cu

Zn

23

96.00

4.00

-

-

 

96.00

2.00

2.00

-

 

96.00

-

4.00

-

22

91.66

8.34

-

-

 

91.66

6.20

2.14

-

 

91.66

4.10

4.24

-

 

91.66

2.00

6.34

-

 

91.66

-

8.34

-

21

87.50

12.50

-

-

 

87.50

10.00

2.50

-

18

75.00

16.00

9.00

-

 

75.00

12.50

12.50

-

 

75.00

11.00

14.00

-

 

75.00

9.50

15.50

-

14

58.50

17.50

24.00

-

 

58.50

15.00

26.50

-

 

58.50

12.50

29.50

-

9

37.50

17.50

42.00

3.00

 

37.50

11.00

51.50

-

 

37.50

10.50

45.00

7.00

 

Typical Composition of Red Gold Alloys

Grades in Carat

Metals, Percent by Mass

Au

Ag

Cu

Ni

Zn

21

87.50

2.50

10.00

-

-

 

87.50

-

12.50

-

-

18

75.00

4.00

21.00

-

-

 

75.00

2.50

22.00

-

-

 

75.00

-

25.00

-

-

14

58.50

7.50

34.00

-

-

 

58.50

6.00

35.00

-

-

 

58.50

5.20

36.30

-

-

9

37.50

7.50

55.00

-

-

 

37.50

-

61.00

-

1.50

 

37.50

5.00

57.50

-

-

 

Typical Composition of White Gold Alloys

Grades in Carat

Metals, Percent by Mass

Au

Ag

Cu

Ni

Zn

Pa

18

75.00

15.00

-

-

-

10.00

 

75.00

8.00

-

-

-

17.00

 

75.00

-

5.00

5.00

-

15.00

 

75.00

11.00

3.10

5.90

-

5.00

 

75.00

-

5.50

14.50

5.00

-

14

58.50

-

18.00

17.50

6.00

-

 

58.50

-

16.50

16.50

8.50

-

 

58.50

31.50

-

10.00

-

-

 

58.50

21.50

5.00

-

-

15.00

 

58.50

18.00

6.50

2.00

1.00

14.00

9

37.50

-

27.60

17.50

17.40

-

 

37.50

-

40.00

10.70

11.80

-

Some Useful Tips to Remember:

1)       24 Karat   -     100 %    -   999 Fine

          22 Karat   -     91.6 %   -   916 Fine

          18 Karat   -     75.0 %   -   750 Fine

          14 Karat   -     58.3 %   -   583 Fine

  2)       01 Tola           = 11.664 gm

          10 Tola           = 116.640 gm

          01 Troy Ounce = 31.104 gm

          01 Kilogram     =  32.150 Tr.Oz

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