THE LEGEND OF METAL

The use of metals in early civilization is closely related. Firstly copper (Cu 銅)and copper alloys were discovered. Then iron(Fe 鐵), silver(Ag 銀), and gold(Au 金) were found and used as hunting and defense tools. They were also used as daily utensils, in decoration and as ornaments. Not only so, were they also currencies, as a medium of payment, as well as storage of wealth.

Metal ores are stored in the earth's crust. We excavate, sort, melt, and chemically treat the ore until it becomes a metal or metal alloy.

Around the fifteen-century, the use of metals in ship building in Europe enabled Columbia to discover the new continent now known to us as America. In that century the numbers of metals known to mankind were only seven in number which included copper, silver, gold, iron, a steel alloy, tin, lead and mercury.

In the nineteen- century, the numbers of metals known to mankind were increased to twenty-three different kinds. And in the beginning of the twentieth-century, the numbers of metals found were significantly increased to sixty-five. Recently a total of seventy kinds of metals and over ten kinds of metal elements and radiation materials were discovered.

HALF METAL & NON-METAL
The advancement of technology in man gives rise more and more as new metals are extracted and new alloys invented. The definition of a metal or a non-metal is changing. Aluminium(Al 鋁) and Sulphur Zinc(Zn 鋅) could be regarded as a half-metal. While Tellurium(Te 碲) and Arsenic(As 砷) under certain conditions are non-metals.

However the chemical composition of these elements are certainly defined as metals.

SOLID AND LIQUID
The general belief of metals is something cold, hard, and requires high temperatures to melt and treat. However, if we are cautious enough, we find these descriptions not to be correct. Let's us think of the Mercury(Hg 汞) in a thermometer. It is a metal in the form of a liquid. Cesium(Ca 銫) could be melted in the palms of our hands. While Lithium(Li 鋰), a new material for batteries, and Lead(Pb 鉛) are so soft that even our finger tips could cut or change it's shape.

HEAVY METALS AND LIGHT METALS
Metals could also be divided into heavy metals and light metals according to its specific gravity. Specific gravity is the density of a material in relationship to a standard material. The standard material for solid and gas are commonly known as water and air.
Sometimes oxygen and hydrogen are also used as a standard.
Any kinds of metals which are five times heavier or lighter is classified as heavy or light metal.

FERRIOUS AND NON-FERRIOUS
Metals could be easily divided into ferrous and non-ferrous metals. Metals with iron, i.e. ferric, are ferric-metal. Common examples are iron, stainless steel, etc. While non-ferric metals include gold, silver, copper etc.

PURE METAL AND ALLOY

Metals could also be classified as a pure metal or an alloy. A pure metal of a hundred percent is quite likely to cost quite a bit as the requirement in technology is tremendous. An alloy is a compound formed by more than two kinds of metals. An alloy usually reduces the cost in meeting the requirements of the strength, conductivity, specific gravity and total weight, surface appearance etc.

RARE METALS

Rare metals are metals which are rare or with low density in the earth's crust. It includes precious metals such as Platinum(Pt 鉑), Palladium(Pb 鈀), Ruthenium(Ru 釕), Osmium(Os 鋨), Rhodium(Rh 銠) etc. Rare Metals includes Lithium(Li 鋰), Cerium(Cs 銫), Beryllium(Be 鈹), Francium(Fr 鈁), Rubidium(Rb 銣) etc. Metals with high melting points includes Titanium(Ti 鈦), Tungsten(W 鎢), Molybdenum(Mo 鉬), Vanadium(V 釩), Rhenium(Re 錸) , and others radiation materials such as Uranium(U 鈾), Radium(Ra 鐳), Polonium(Po 釙) etc.