Material

Gold belongs to the group of precious metals. The Latin name of gold is Aurum, which means the light of dawn, and from this the gold has got its chemical notation Au. It has always been an important metal and has during thousands of years been used as means of payment, a stable value of assets and for making jewels.
Gold is the smoothest of all metals. You can draw one gram of gold to a 3.000 meter long thread with a diameter of only 0,00012 mm. Gold  can also be rolled out to a thin sheet, gold foil, with a thickness of only 0,00014 mm.
Gold is one of the heaviest metals, the density is 19,32. Gold is actually nearly twice as heavy as lead.
Gold melts at 1.063 degree Celsius.   
Most of the gold is used in the jewelry industry. Some is used in the dental industry and the rest is used in the electronic industry. In nature you can find gold in grains and nuggets in the bottom sediment of the water streams and in veins in rocks.

Carat

The purity of the gold is measured in carat or thousandth. Pure gold is 24 carat (24k) or 1000.
For making jewelry, 24 carat pure gold is too soft. But you can alloy the gold with other metals, for ex copper to make the metal more strong and durable or silver. If the alloy includes 75% of pure gold, it will be marked 18k or 750. If the alloy includes 58,5% of pure gold, it will be marked 14k or 585. The color of the gold can also be changed depending on what metal you put into the gold, for ex the gold will be redder if you alloy it with copper.

Cleaning

Please clean you gold ring often. Use some warm water and some washing-up detergent and brush it gently with an old tooth brush. If you have a plain gold ring your can go to your local goldsmith or jewelry shop now and then and they can polish your ring and it will be as new again.