Earth

How many minerals do we know?

In nature there are many minerals: around 2000 species are known. Some of them are very rare, while some others are very popular. But only around thirty of them compose the Earth’s crust rocks.  
These minerals are made up of several chemical elements that distinguish them. According to their chemical composition, minerals are classified into the following groups:

• silicates are very important: only 8% of the minerals that compose the Earth do not belong to this group. These minerals are always made of silicon and oxygen, which can bind with aluminium, iron, calcium, magnesium, sodium and potassium. A very important mineral that is present in the deepest layers of the Earth is olivine, which has a very compact and dense structure, as is made of silicon, magnesium and iron. Asbestos, mica, clay minerals, quartz, feldspars (like orthoclase and plagioclase) belong to this group
• the group of carbonates is made up of two important minerals: calcite, a calcium carbonate that forms calcareous rocks and dolomite, a calcium and magnesium carbonate that forms dolomite rocks. These minerals and their corresponding rocks melt in water, and form karstic landscapes and dolomitic mountain landscapes
• in particular environmental conditions, the evaporation of sea or lake water leads to the creation of chalk or rock salt (kitchen salt). This is the group of sulphates and salts
• when oxygen binds to other elements such as iron, oxides and hydroxides are formed. Some examples are magnetite, limonite, haematite, which form rocks with a yellow-red colour, and represent the main iron source of the mining industry
• other important mineral deposits are represented by sulphides, minerals containing sulphur and iron, like pyrite. Sulphur together with iron and copper leads to chalcopyrite. Sulphur together with lead originates galena, while sulphur and mercury results in cinnabar
• gold,silver and copper are deposits made of only one element. This is why they are called native elements. Both diamond and graphite are exclusively made of carbon, but they differ from the commercial and crystal structure point of view, as explained in the corresponding paragraph.