Rare elements with high economic value are called precious metals. Chemically, precious metals have less reactivity than other elements, and have higher luster and melting points. Precious metals were as important as money in history, but today they are seen more as an investment tool or used for industrial purposes.
The most well-known precious metals are gold and silver. In addition to their industrial use, they are mostly used in jewelry. It can be list other precious metals in the platinum group as follows: ruthenium, rhodium, palladium, osmium, iridium, and platinum.
The only reason for the demand for precious metals should not be their use, but also an investment tool. As of January 2007, palladium is worth almost half of gold, and platinum is worth about twice that of gold. Silver is the cheapest among them. Rhodium is the world’s most expensive precious metal.
Gold is a soft, bright yellow metallic element denoted by the symbol Au in chemistry. The bright yellow color of gold, its resistance to acids, its free presence in nature and its easy processing have attracted the attention of people since ancient times. Gold is a very heavy metal that catches the eye with its bright yellow color and sparkle. Moreover, since it is a very stable element that does not react easily, it is not affected by air and water. Therefore, it never rusts, tarnishes, or becomes dull. Another feature is that it is very soft in its pure state; therefore, it can be easily hammered into shape. With all these features, gold has been considered one of the most valuable metals throughout history.
Gold is found in low concentrations in a large part of the world. It constitutes an estimated 0.001 ppm (one millionth) of the earth’s globe. Trace amounts can be found in copper and lead minerals as well as calaverite (Au2Te4), sylvanite (Au2Ag2Te6) and krennerite (Au8Te6) minerals. It is found in volcanic quartz, in the sandy beds of streams, as dust and ingots.