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There is no specific definition for Gold, as its importance is known worldwide. Gold is considered to be one of the precious metals from the rest. Many people are engaged in investing the Gold. Gold has always been attraction to the masses be it Men or Women. Ancient Egyptian hieroglyphs represent gold with the brilliance of the sun. Gold is the best form of money the world has ever known.

Gold has shown its prominence in our history and continues to hold its importance in the current era too. Ancient age claims about 1, 30,000 tones of gold in the earths crust however it has been excavated to a huge amount since then till date. According to the statistics in order to extract a single ounce (31.104 gms) of gold about 17 tons of ore has to be mined.  

The availability of gold is beneath the earth’s crust, in the seas, rivers and plants. Gold is also available in veins and secondary alluvial deposits as either free metals or in combined state in nature. Gold can also be regained from Silver and Copper refining. In order to recover this gold from the earth, the techniques used are placer mining, panning and open pit mining.
The top five countries producing gold are South Africa, USA, Australia, Russia and Canada.

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
24K
95.83%
958 Fine
23K
91.6%
916 Fine
22K
87.6%
875 Fine
21K
75.0%
750 Fine
18K
58.3%
583 Fine
14K
37.5 %
375 Fine
9K
 
Percent : Parts of gold per 100
Fineness : Parts of gold per 1000
Karat : Parts of gold per 24

Point to be noted:

Karat and Carat are two different things, Karat is basically a unit to measure the purity of metal while carat is usually a unit to measure the weight of precious stones and gems.

Effects of Acids on Metals

•  Gold can only be affected in the presence of oxidizing agent; otherwise no acid can dissolve or attack gold.
•  Gold dissolves in Aquaregia (1 part of Nitric Acid and 4 parts of Hydrochloric Acid)
•  Potassium Cyanide in presence of oxidizing agent dissolves gold.
•  Gold is attacked by alloy of silver, copper or zinc.
•  Silver dissolves in Nitric Acid
•  Platinum is resistant to almost any acid.

Silver is attacked by the atmosphere and atmospheric pollution while Gold and Platinum have no effect of atmosphere and atmospheric pollution on them. Gold and Platinum do not get rusted, tarnished or corroded.
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
18
Au
Ag
Cu
Ni
Zn
Pa
75.00
15.00
-
-
-
10.00
75.00
8.00
-
-
-
10.00
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 :
24 Karat     
100 %    
999 Fine
22 Karat     
91.6 %   
916 Fine
18 Karat     
75.0 %   
750 Fine
14 Karat     
58.3 %   
583 Fine
09 Karat     
37.5 %   
375 Fine
 
 
 
 
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