Formed

The most common natural method of concentration of gold is through the ancient action of hot fluid inside the Earth's crust.

The fluids moved through the rocks over a large area and "dissolved" the gold. When these fluids cooled or reacted with other rocks the dissolved gold precipitated (came out of the fluid) in cracks or fractures forming veins. If the fluids move over a large enough area, and dissolve the gold for a long enough period of time, gold can be concentrated in amounts in the parts per thousand or even greater.

As well as gold, the fluids carried other dissolved minerals, such as quartz. This is why gold is often found with quartz. These are known as primary gold deposits and to extract the gold the rock containing the veins of gold has to be dug up (mined), crushed and processed.

The rocks containing the gold veins have now been exposed on the surface and are eroding away. The gold that these rocks contained has been washed down into creeks to form alluvial gold deposits. Here, the gold is further concentrated by the action of water. Because gold is heavier than most of the material moved by a creek or river, it can become concentrated in hollows and trapped in the bed of the river. These are known as secondary gold deposits.

Properties
Gold is a very rare substance making up only five ten-millionths of the Earth's outer layer. Its rarity and its physical properties have made it one of the most prized of Earth's natural resources.

Gold, like iron, copper, lead, tin etc. is a metal. Metals are good conductors of heat and electricity and are almost all solid at room temperature (with the exception of mercury). They are malleable and ductile.

Gold is heavy — it weighs over nineteen times more than water, and is almost twice as heavy as lead.

Gold is quite soft. It is slightly harder than a fingernail but not as hard as a coin or glass.

Gold, like most metals, can be hammered into thin sheets (malleable ) or drawn out into thin wires (ductile).
This has made gold sought after for a wide range of applications, like jewellery and in electronics. Gold leaf" for example, is gold that has been beaten into a sheet less than one tenth of a millimetre thick. It is then used for lettering on honour rolls in schools, or for putting gold onto picture frames and ornaments.

Chemical Symbol:
Au
Mineral:
usually found as a native metal
Relative Density:
19.3
Hardness:
2.5–3 on Mohs Scale
Malleability:
High
Ductility:
High
Melting point:
1060°C
Boiling point:
2660°C
Atomic Mass:
196.97